Analog electronics 200 questions
1. What are characteristics of electronic devices made of semiconductor materials compared to traditional vacuum electronic devices?
Answer: Good frequency response, small size, low power consumption, handy for pocket ICs, and outstanding strength, shock resistance and reliability, but inferior to vacuum devices in terms of distortion and stability. 2. What are intrinsic semiconductors and extrinsic semiconductors? Answer: Pure semiconductors are intrinsic semiconductors, and they tend to be medium value elements in periodic table of elements. Impurity semiconductors are obtained by doping impurity elements with high or low valence in a very small proportion in intrinsic semiconductor. 3. Is a hole a carrier? Does an electron move when a hole conducts electricity?Answer: No, but it can be equivalent to a carrier in its motion. When a hole conducts electricity, electrons with same charge will move in opposite direction. 4. When obtaining doped semiconductors, what ratio is usually used to dope intrinsic semiconductors? Answer: Include in a ratio of one part per million.
5. What is an N-type semiconductor? What is a P-type semiconductor? What happens when two semiconductors are bonded together?Answer: A semiconductor in which majority of carriers are free electrons is called N-type. semiconductor. Conversely, a semiconductor in which most of charge carriers are holes is called a P-type semiconductor. A P-N junction will be formed after connecting a P-type semiconductor to an N-type semiconductor. 6. What is main physical characteristic of a PN junction? Answer: One-way conduction and more sensitive temperature characteristics. 7. What other names are there for a PN connection? Answer: space charge region, blocking layer, depleted layer, etc. 8. Are terminal voltage and current applied to a PN junction linear? Why does it have unidirectional conduction?Answer: It is non-linear. electric field generated by forward voltage, causing a recombination phenomenon, which leads to a thinning of barrier layer, and forward current increases exponentially with increasing voltage. When voltage is applied, situation is exactly opposite of that described above, barrier layer becomes thicker, current is almost completely zero, and a cut-off state appears macroscopically. . This is a unidirectional conductance characteristic of a PN junction. 9. Is there really no current when a reverse voltage is applied to a PN junction?Answer: There is no current at all, and minority carriers are under action of a reverse voltage current. 10. What are fundamentalsnye technical parameters of diodes? Answer: Maximum rectified current11. What are main applications of diodes? Answer: rectification, detection, voltage stabilization, etc. 12. How does transistor control collector current?Answer: through current distribution ratio. 13. Can two diodes be turned into a triode? Why? Answer: No, two diodes are connected back to back through metal electrodes, and base area required for a triode is not formed. 14. What is triode penetration current? How does this affect amplifier? Answer: When base is open, current between collector and emitter is penetration current: where collector-base reverse leakage current, and is generated by movement of minority carriers, so it is very sensitive to temperature, both will increase sharply with increasing temperature. Thus, it adversely affects amplifier. Therefore, in real work, they should be as small as possible. 15. What is triode gate voltage? Answer: A silicon tube usually has a voltage of 0.5 V. A germanium tube is about 0.2 V. 16. Is an amplification circuit that amplifies an electrical signal same as a magnifying glass that magnifies an object? Answer: Not same. 17. What are basic bias conditions in a triode amplifier? Answer: The emitter junction is forward biased, collector junction is reverse biased. 18. How many areas are usually divided into input and output characteristics of triodes? Answer: Usually it is divided into gain zone, saturation zone and cutoff zone. 19. How many basic configurations are there for an amplifier circuit? What are they?Answer: Three types, namely common emitter, common base and common collector. 20. In a common-emitter amplifier circuit, what types of bias circuits are commonly used? Answer: There is an upper base displacement, partial pressure and feedback on a given basis. 21. How important is definition of static operating point for an amplifier? Answer: Proper determination of static operating point can result in amplifier having minimal cutoff and saturation distortion, and at same time can obtain maximum dynamic range and triode efficiency. 22. In what area should static operating point of amplifier be located on input and output characteristics of triode? Answer: Usually it should be in center of amplification region of input and output characteristics of triode. 23. When drawing DC path of an amplifier, should I pay attention to power supply and capacitors? Answer: The capacitor should be considered as an open circuit, and power supply should be considered as an ideal power source. 24. Which amplifiers are suitable for graphical amplifier method? Answer: It is generally suitable for single-tube common-emitter amplifiers and intop-biased base and push-pull power amplifiers. 25. What does DC load line and AC load line mean in amplifier schematic method? Answer: The DC load line defines parameters of DC path in static state. The value of AC load line is to analyze maximum effective amplitude and waveform distortion at output of amplifier in presence of an AC signal. 26. How to evaluate performance of an amplifier circuit? What are main indicators?Answer: The performance of an amplifier circuit is generally determined by following indicators: gain, input and output impedance, bandwidth, distortion, signal-to-noise ratio. 27. Why is decibel often used as unit of amplifier voltage gain? What does it have to do with multiples? Answer: The reason decibels are often used as unit of voltage gain of an amplifier is: (1) The value becomes smaller, which is convenient for reading and writing. (2) Easy to operate. (3) It matches ear and is easy to appreciate. 28. Is bandwidth of amplifier as wide as possible? Why? Answer: No! The bandwidth of amplifier is not as wide as it should be. The key is to see if amplifier has special requirements for frequency of signal it is working with! For example, a frequency selective amplifier requires a narrow bandwidth, while a conventional audio amplifier requires a relatively wide bandwidth. 29. What effect does input and output impedance of an amplifier have on amplifier? Answer: The higher input impedance of amplifier, better, so that effective output of input source can be improved, and effective signal consumed by internal resistance of signal source can be reduced to a minimum. range. The output impedance should be as low as possible, which can increase effective output signal ratio at load. 30. What is principle by which input and output impedance is chosen when designing an amplifier? Answer: High income and low productivity. 31. How many types of amplifier distortion are usually divided into? Answer: Single-tube AC small signal amplifiers usually have three types: saturation distortion, cutoff distortion and non-linear distortion, and push-pull power amplifiers can also have crosstalk distortion. 32. What kind of distortion will be caused by an amplifier operating point that is too high? Operating point too low? Answer: Saturation distortion, cutoff distortion33. What are main causes of harmonic distortion in an amplifier? Answer: When operating point falls into non-linear region of input characteristic, and minimum value of input signal is not equal to zero, this causes non-linear distortion. 34. What is difference between microv methodariational analysis of equivalent circuit and a graphical method of analysis of amplifiers? Answer: You can more conveniently and accurately calculate input and output impedance, voltage gain, etc. of amplifier. The graphical method can intuitively analyze if amplifier's operating point is set correctly, what kind of distortion will be generated, as well as dynamic range. 35. What are general steps for amplification circuit analysis using microvariance equivalent circuit analysis method? Answer: 1) Calculate point Q; 2) Calculate triode using formula; 3) Use microvariable equivalent circuit to draw AC circuit of amplifier; 4) Calculate amplifier according to 3) and corresponding formula Input and output impedance, voltage gain, etc.36. What is scope of equivalent circuit analysis method with microvariations? Answer: Suitable for analysis of any simple or complex circuit. So far, amplifying device mainly operates in linear range. 37. What are limitations of method of analysis of equivalent circuits with microvariations? Answer: It can only solve problem of calculating AC component, and can not be used to determine Q point, and also can not be used to analyze harmonic distortion and maximum output amplitude and other problems. 38. What are main factors affecting stability of operating point of an amplifier? Answer: Temperature drift of components, fluctuations in power supply, etc. 39.What method is commonly used to stabilize operating point in a common-emitter amplifier circuit? Answer: Enter current series of negative reviews. 40. Why can't single tube amplifier circuit meet requirements of different performance?Answer: The amplification power is limited, according to input and output impedance, it can't take into account good match between amplifier and outside world at same time. 41. What is main purpose of a communication chain? Answer: Let useful AC signal pass smoothly between front and rear amplifiers and at same time provide good static isolation. 42. How many ways are there for interstage communication of multistage amplifier circuits? Answer: As a rule, there is a resistive-capacitive connection, a transformer connection and a direct connection.43. What is total voltage gain in a multi-stage amplifier circuit?Answer: Yes. is equal to product of payoffs of all stages. 44. What is input and output impedance of a multistage amplifier circuit? Answer: They are equal to input resistance of first stage and output resistance of last stage, respectively. 45. What are special problems of feed-forward amplifier circuits? How to solve them?Answer: Zero drift is biggest problem of feed-forward amplifier circuits. The most fundamental solution is to use a differential amplifier. 46. PocheSo three stages is most common amplifier design?Answer: too few stages are not enough for amplification, and too many stages make it difficult to solve problems such as zero drift. 47. What is zero drift? What are main factors causing it? What is most basic of them? Answer: When input signal of amplifier is zero, output is still slow and uneven output signal. The main reason for this phenomenon is that parameters of circuit elements fluctuate due to influence of temperature, resulting in instability of Q point. In a multi-stage amplifier, due to feed-forward method, fluctuation of Q point will be transmitted and amplified step by step. 48. What is feedback? What is DC and AC feedback? What is positive and negative feedback?Answer: A phenomenon in which an output signal is sent back to an input terminal through a certain way and processed by an amplifier called feedback. If signal is DC, it is called DC feedback, if signal is AC, then it is called AC feedback. After reprocessing, final output of amplifier is greater than before introduction of feedback, which is called positive feedback. Conversely, if final output of amplifier is greater than before introduction of feedback, this is called positive feedback, less, this is called negative feedback. 49. Why introduce feedback?Answer: Generally speaking, to improve performance of amplifier The introduction of positive feedback is necessary to increase sensitivity of amplifier to weak signals or increase gain; while introduction of negative feedback is to improve amplifier gain stability and operating point stability, reduce distortion, improve input and output impedance, broaden bandwidth, and so on. 50. What are four configurations of AC negative feedback?Answer: There are four configurations: series current connection, parallel current connection, series voltage connection, and parallel voltage connection. 51. What is general expression for an AC negative feedback amplifier circuit?Answer: N/A52. What will happen to performance after introduction of series negative current feedback? into amplifier circuit What effect?Answer: It can weaken voltage gain, improve its gain stability, reduce distortion, increase input impedance, increase output impedance, etc. 53. After negative voltage feedback is introduced into amplifier circuit, what effect will this have on performance?Answer: This may weaken voltage gain,improve gain stability, reduce distortion, reduce input impedance, reduce output impedance, etc. 54. After introducing parallel negative current feedback into amplifier circuit, what effect will it have on performance?Answer: It has a debilitating effect on voltage gain, can improve its gain stability. , reduce distortion, reduce input impedance, improve low output impedance, etc. 55. After parallel negative voltage feedback is introduced into amplifier circuit, what effect will it have on performance?Answer: Attenuates voltage gain, can improve its gain stability, reduce distortion, lower input impedance, lower output etc. 56. What is deep negative feedback How to evaluate gain under condition of deep negative feedback?Answer: In a feedback amplifier, if average ≫1, then amplifier that satisfies this condition is called a deep negative feedback amplifier, feedback gain The coupling of an amplifier is now completely determined by feedback factor. 57. The deeper negative feedback, better? What is self-oscillation? Which feedback amplifier circuit is subject to self-oscillation? How to eliminate self-oscillations? Answer: no. When feedback gain of a negative feedback amplifier circuit = 0, it means that circuit has an output when input value is 0, and circuit is said to have self-excited oscillations. When signal frequency enters low or high frequency band, due to additional phase shift, negative feedback amplifier circuit is subject to self-oscillation. To eliminate self-oscillations, it is necessary to destroy conditions for occurrence of oscillations, change frequency characteristics of AF and produce it. 58. Can only negative feedback be introduced into an amplifier circuit? Can positive feedback be introduced into an amplifier circuit to improve performance?Answer: No. It can, for example, a bootstrap circuit, introduce an appropriate positive feedback while also introducing negative feedback to increase input resistance. 59. What amplifier configuration is a voltage follower? Can it amplify input voltage signal? Answer: A voltage follower is a series voltage amplifier. It cannot amplify input voltage signal. 60. What type of feedback amplifier is a voltage follower? Answer: A voltage follower is an amplifier with serial voltage feedback. 61. Where is main application of voltage follower? Answer: The main purpose of voltage follower: it is usually used in input and output stagesmulti-stage amplifier circuit, and can also be connected to two circuits as a buffer. 62. What about input and output characteristics of voltage follower? Answer: Input and output characteristics of voltage follower: input impedance is high, output impedance is low. 63. Generally speaking, how many types of power amplifiers are there? Answer: According to conduction angle of transistor in whole cycle, it can be divided into class A, class B, class A and B, class C and class D. According to different circuit structures, it can be divided into transformer coupling, without OTL output transformer , no output capacitor OCL and bridged push-pull BTL power amplifier circuit. 64. What are characteristics of class A and class B power amplifiers? Answer: Class A power amplifier characteristics: transistor is on during entire signal cycle, power consumption is large, and distortion is small; class B power amplifier characteristics: transistor only turns on in half a period of signal, low consumption, large distortion. 65. Why does a class B power amplifier create crossover distortion? How to overcome it? Answer: Since there is a turn-on voltage Uon between transistors b-e, when input voltage is |ui| 66. Why is it important to consider power consumption, lamp consumption and efficiency when designing a power amplifier? Answer: Because power amplifier circuit produces maximum possible power when detecting supply voltage. 67. In terms of feedback, what type of circuit is an oscillator? Answer: In terms of feedback, oscillator is an amplifier circuit with positive feedback. 68. What are initial conditions for sinusoidal oscillations? Answer: Initial condition for sinusoidal oscillations. 69. How to form a sinusoidal oscillatory circuit? What parts should it include? Answer: Composition of a sinusoidal circuit: amplifier circuit, frequency selection circuit, positive feedback circuit, amplitude stabilization link. 70. How to determine if circuit can begin to vibrate in a transformer-coupled sine-wave generator? Answer: A method for assessing whether a circuit can start to oscillate in a transformer-coupled sinusoidal generator: instantaneous polarity method. 71. How to determine if circuit can start to vibrate in a three-point sinusoidal generator? Answer: In a three-point sine-wave generator, method for assessing whether circuit can start to oscillate is to shoot at same base and reverse. 72. What is frequency response (or frequency response) of amplifier circuit? Answer: The steady-state performance response of an amplifier circuit (mainly related to voltage gain Au) to a sinusoidal input of various frequencies is called frequency response of amplifier circuit. 73. Classification of frequency characteristics. Answer: Frequency characteristics are divided into amplitude-frequency characteristics and phase-frequency characteristics. 74. What is frequency response? Answer: An amplitude-frequency characteristic is such a characteristic that gain value (that is, ratio of input and output sinusoidal voltage amplitudes) changes with frequency. 75. What is phase response? Answer: Phase response refers to The phase difference between input voltage and input voltage (that is, phase shift of signal voltage by amplifier circuit) depends on frequency. 76. What is a Bode plot? Answer: When frequency response curve takes logarithmic coordinates, it is called a Bode plot. 77. Why use a Bode diagram to express frequency response? Answer: Because when studying frequency response of amplifying circuit, frequency range of input signal is often set from units of Hz to millions of megahertz, and gain of amplifying circuit can range from several times to millions of megahertz. once; such a wide range of change is represented in coordinate system, so logarithmic coordinates are used, that is, Bode plots. 78. What is upper cutoff frequency of amplifier circuit? Answer: When signal frequency is raised to a certain level, boost value will also decrease, and frequency at which boost value is 0.707 times |Am| is called upper limit cutoff frequency fH. 79. What is lower limiting cutoff frequency of amplifier circuit? Answer: When frequency of signal is reduced to a certain level, increase value will also decrease, and frequency at which increase value is 0.707 times |Am| is called lower limit cutoff frequency fL. 80. What is a half power point? Answer: When signal frequency is upper limit cutoff frequency fH or lower limit cutoff frequency fL, output voltage gain |Am| drops to 0.707 times |Am|, i.e. corresponding output power also drops to half amplitude, so fH or fL is also called half power point. 81.What is bandwidth of amplifier circuit? Answer: The frequency band formed between fH and fL is called bandwidth BW of amplifier circuit, which can be expressed as BW=fH－fL. 82. What happens if frequency response of an amplifier circuit is bad? Answer: If frequency response of amplifier circuit is not satisfactory when input signal is not a sine wave, output waveform will be different from input waveform, that is,There is distortion of waveform, which is called frequency distortion. Among them, frequency distortion caused by poor frequency response, that is, different frequency amplification, is called amplitude distortion; The frequency distortion caused by poor phase response, i.e. phase shift is not proportional to frequency, is called frequency distortion. called phase distortion. 83 What are main factors that affect frequency response of low frequency amplifier circuits? Answer: The frequency response of low frequency amplifier circuit is mainly affected by following factors: (1) The more stages of amplifier circuit, narrower bandwidth and worse frequency response. (2) Introduction to negative feedback circuit can expand bandwidth and improve frequency response. (3) The coupling capacitance, output impedance of preamplifier circuit, and input impedance of postamplifier circuit also affect frequency response. 84.What are characteristics of frequency characteristics of treble circuit? Answer: The amount of gain of high-pass circuit decreases in low-frequency band, which leads to a phase shift. 85.What are frequency characteristics of low-pass circuit? Answer: The LPF gain decreases in high frequency band, a delayed phase shift occurs. 86. For an amplifier circuit, wider bandwidth, better? Answer: For an amplifier circuit, wider bandwidth, better. 87. What is a power amplifier circuit? Answer: Power amplifier circuit refers to an amplifier circuit that can output enough power to drive a load. Since it is usually located in last stage of a multi-stage amplifier circuit, it is often referred to as final amplifier circuit. 88. What are requirements for main technical characteristics of power amplifier circuit? Answer: The power amplification circuit is a large signal amplification circuit, and its main technical requirements are: ⑴The output power must be large enough; ⑵ Conversion efficiency must be high; ⑶The power consumption of triode should be small; non-linear distortion should be small; ⑸ The operation of triode must be safe and reliable. 89. What method is used to analyze power amplifier circuit? Answer: Since power amplifier circuit operates under strong signal conditions, weak signal equivalent circuit analysis method is not suitable for analysis. Generally, analysis uses large signal model or graphical method, and more uses graphical method. 90. What is working condition of class A triode? Answer: In an amplifying circuit, when input signal is a sine wave, if triode is on during entire signal cycle (i.e. conduction angle θ=360°), it is said to be operating in a class A state. 91. What is working condition of class B triode? Answer: In cxIn terms of gain, when input signal is a sine wave, if triode conducts only in positive half-cycle or negative half-cycle of signal (that is, conduction angle θ = 180°), it is said to operate in state B. 92. What is working condition of class A and B triode? Answer: In amplifying circuit, when input signal is a sine wave, if conduction time of triode is more than half a period and less than a period (that is, conduction angle θ=180°～360°), it is called Class A and B status operation. 93. What is a transformer coupled power amplifier circuit? Answer: A power amplification circuit with an input coupling transformer and an output coupling transformer is called a transformer coupled power amplification circuit. 94. What are advantages and disadvantages of a transformer coupled power amplifier circuit? Answer: The advantage of transformer coupled power amplifier circuit is that it can realize impedance conversion, and disadvantage is that it is bulky, heavy, consumes non-ferrous metals, has low frequency and low power. frequency and high-frequency characteristics are poor. 95. What is an OCL chain? Answer: The OCL circuit refers to a power amplifier circuit without an output coupling capacitor. 96. What are advantages and disadvantages of OCL scheme? Answer: The OCL circuit has advantages of small size, light weight, low cost and good frequency response. But this requires two sets of symmetrical positive and negative power supplies, which is not convenient enough in many cases. 97. What is an OTL chain? Answer: The OTL circuit is a power amplifier circuit without an output coupling transformer. 98. What are advantages and disadvantages of overhead line scheme? Answer: The advantage of OTL scheme is that only one power supply is required for power. The disadvantage is need for a large capacitor, able to turn a group of power supplies into two symmetrical positive and negative power supplies, low frequency performance is poor. 99. What is a BTL Schema? Answer: To realize a single power supply without transformers and large capacitors, you can use a push-pull power amplifier bridge circuit called BTL circuit. 100. What are advantages and disadvantages of BTL scheme? Answer: The advantage of BTL circuit is that it only needs one power supply, no transformers and large capacitors are needed, and output power is high. The disadvantage is that number of lamps used is large, it is difficult to achieve perfect symmetry of characteristics of lamps, total lamp losses are high, and conversion efficiency is low. 101. What is most widely used power amplifier circuit today? Answer: The most common power amplifier circuits are OTL and OCL circuits. 102. What is a crossoh distortion? Answer: Only when |Ui|>Uon, triode turns on. When input signal Ui crosses zero, output signal will be distorted. This distortion is called crossover distortion. 103. How to eliminate crossover distortion? Answer: In order to eliminate crosstalk, it is necessary to set an appropriate static operating point so that both transistors operate in a state of critical conduction or microconduction. 104. For an OCL power amplifier circuit, how to estimate maximum output power of circuit when power supply voltage and load resistance are known? Answer: Maximum output power of OCL power amplification circuit: 105. For an OCL power amplification circuit, how to estimate power provided by circuit's power supply when supply voltage and load resistance are known? Answer: The power provided by power supply of power amplifier circuit OCL: 106. For an OTL power amplifier circuit, how to estimate maximum output power of circuit when supply voltage and load resistance are known? Answer: The maximum output power of overhead line power amplification circuit: 107. For an overhead line power amplification circuit, how to estimate power provided by power supply of circuit when power supply voltage and load resistance are known? Answer: The power provided by power supply unit of overhead line power amplification circuit: 108. When choosing transistors in a power amplification circuit, what parameters should I pay special attention to? Answer: When choosing a transistor in a power amplifier circuit, special attention should be paid to parameters: maximum voltage drop on lamp that transistor can withstand, maximum collector current and maximum power consumption. 109. What is maximum undistorted output voltage of power amplifier circuit? Answer: The maximum undistorted amplitude of output voltage of power amplifier circuit is equal to supply voltage minus saturation voltage drop of transistor, namely: Uom=Vcc-UCES. 110. What is maximum output power of power amplifier circuit? Answer: The maximum output power of a power amplifier circuit refers to When voltage is a sine wave and output signal is basically undistorted, maximum AC power can be obtained at load. Namely: Pom=Uo×Io. 111. What is conversion efficiency of power amplifier circuit? Answer: The conversion efficiency of a power amplifier circuit refers to ratio of maximum output power to power provided by power supply. Namely: η=Pom/Pv. 112. Please briefly describe steps of power amplifier circuit analysis. Answer: Due to large amplitude of input signal of power amplifier circuit, analysis should use a graphical method. Generally, analysis is carried out according to following steps: (1) find amplitude Uom of AC voltage, whichth can be obtained on load of power amplifier circuit, (2) find maximum output power of Pom circuit; (3) Find average DC power Pv provided by power supply, (4) Find conversion efficiency n. 113. What is a power amplifier lamp failure? Answer: Power amplifier lamp breakdown refers to phenomenon of a sudden increase in collector current when voltage between CE and CE of transistor increases to a certain value. 114. What is secondary power amplifier lamp failure? Answer: The second breakdown of power amplifier lamp means that after first breakdown of transistor, if collector current is not limited, operating point of transistor will change at a high rate, so current will increase. sharply and voltage drop across tube will decrease Phenomenon. 115. How to choose a transistor in a power amplifier circuit? Answer: When choosing transistors, limit parameters should be UCEO>2Vcc, ICM>Vcc/RL, PCM>0.2Pom. 116. When does a transistor dissipate most power? Answer: At Uom=2Vcc/π≈0.6Vcc, PT=PTMAX, that is, power dissipation of transistor is highest. 117. What is zero drift phenomenon? Answer: The phenomenon when input voltage is zero, but output voltage is not zero and changes slowly, is called zero drift phenomenon. 118. What is temperature drift? Answer: When input voltage is zero, phenomenon that output voltage is not zero and changes slowly due to change in semiconductor device parameters caused by temperature changes is called temperature drift. This is main reason for zero drift. 119. What are zero drift suppression methods? Answer: Zero drift suppression methods: ⑴Introducing DC negative feedback circuit; ⑵The use of temperature compensation method, use of thermistor to compensate for replacement of amplifier tube; ⑶Using "differential amplifier circuit". 120. What is special problem of feedforward amplifier circuit? How to decide? Answer: A particular problem of feed-forward amplifier circuit is phenomenon of zero point drift. The solution is to use a differential amplifier circuit. 121. What is function of a differential amplifier circuit? Answer: The differential amplifier circuit can amplify differential mode signal and suppress common mode signal. 122. What is relationship between common mode signal and zero drift and temperature drift? Answer: Temperature drift is main cause of zero drift, therefore, generally speaking, zero drift refers to temperature drift. For a differential amplifier circuit, temperature change is effectively equivalent to a common mode signal. 123. What are characteristics of circuit structure of a differential amplifier circuit? Answer: The differential amplifier circuit consists of two triodes, and parameters of all components of circuit are symmetrical. 124. What is a differential mode signal? Answer: The differential mode signal is difference between two input signals. That is: 125. What is an in-phase signal? Answer: Common mode signal is arithmetic mean of two input signals. Namely: 126. What is Differential Mode Gain? Answer: Differential mode gain refers to ratio of output signal to input signal when a differential mode signal is applied to input. Namely: 127. What is common mode gain? Answer: Common mode gain refers to ratio of output signal to input signal when a common mode signal is applied to input. That is: 128. What is total output voltage of differential amplifier circuit? Answer: The total output voltage of differential amplifier circuit is: 129. What is overall mode deviation factor? Answer: The common mode rejection ratio indicates ability of a differential amplifier circuit to amplify a differential mode signal and ability to suppress a common mode signal. It is written as KCMR, and its definition is: 130. Differential Amplifier Circuit What are four connections? Answer: According to different ground conditions of input and output terminals, differential amplifier circuit is divided into four types: double input and double output, double input and single output, single input and double output, and single input and output. one way out. 131. In a differential amplifier circuit, when a common-mode signal is applied to input, what is equivalent emitter resistance for each side of transistor? Answer: Equivalent emitter resistance is equal to 2Re. 132. In a differential amplifier circuit, when input signal is differential mode, what is equivalent emitter resistance for each side of transistor? Answer: The emitter is equivalently grounded. 133. In a differential amplifier circuit with a two-output connection method, when a differential mode signal is input, for transistors on each side, what is equivalent load resistance connected between output terminals of two transistors? Answer: Equivalent load resistance is 1/2RL. 134. Will input impedance change in a four-terminal differential amplifier circuit? Answer: The input impedance will not change. 135. Will output impedance change in a four-terminal differential amplifier circuit? Answer: The output impedance of a two-output connection is twice that of a one-output connection. 136. Will gain of differential mode change in a differential amplifier circuit with four connections? Answer: The differential gain with dual output connection is twice that of single output connection. 137. What are common current source circuits? Answer:Common current source circuits include: a mirror current source circuit, a proportional current source circuit, and a microcurrent source circuit. 138. What is function of current source circuit in amplification circuit? Answer: The role of current source circuit in amplification circuit: ⑴provide a stable bias current for amplifying tube;⑵as a resistive load instead of a high-resistance resistor. 139. What are characteristics of mirror current source circuit structure? Answer: A mirror current source circuit consists of two lamps with exactly same characteristics. The base and collector of one lamp are connected together to connect to a power source, while emitters of two lamps are not connected with resistance. 140. What are characteristics of proportional structure of current source circuit? Answer: A proportional current source circuit consists of two lamps with same characteristics, base and collector of one lamp are connected to a power source, and emitters of two lamps are connected by resistors. . 141. What are characteristics of microcurrent source circuit structure? Answer: The microcurrent source circuit consists of two lamps with same characteristics, base and collector of one lamp are connected to a power source, emitter of other lamp is connected to a resistor. 142. What is an Integrated Operational Amplifier? Answer: The integrated operational amplifier is a DC amplifier with a large gain. 143. What are characteristics of frequency response of an integrated operational amplifier? Answer: The frequency characteristics of integrated operational amplifiers have low-frequency characteristics, and upper limit of cutoff frequency is low, usually within 1M. 144. What is input impedance, output impedance, and open-loop voltage increase of an integrated op amp? Answer: The input resistance Rid of integrated operational amplifier is very large, usually more than 108 ohms, output resistance Rod is very low, its value is from tens to hundreds of ohms, usually less than 200 ohms; open-loop voltage gain Aud is very large, its value exceeds 106. 145. What is an ideal operational amplifier? Answer: An idealization of characteristics of an integrated op-amp is an ideal op-amp, ie Rid®∞, Rod®0, Aud®∞, etc. of an ideal op-amp. 146. What are characteristics of a linear application of an ideal operational amplifier? Answer: When an ideal op-amp is applied linearly, two input terminals are virtual short (un=up) and virtual open (in=ip=0). 147. What are conditions for a linear application of an ideal operational amplifier? Answer: As long as uid=up-un is small, ideal op-amp is in a state of linear application. As a rule, since Aud of an ideal op amp is very large, if you add a negativefeedback, it must be deep negative feedback, and ideal op-amp will be in linear state of application. Of course, there are other cases of linear application states. 148. Integrated op amps can be used in almost every aspect of analog circuits. Let me illustrate this with some examples. Answer: Integrated operational amplifiers can implement various operational circuits, such as proportional converters, adders, subtractors, differentiators and integrators. 149. Integrated op amps can be used in almost every aspect of analog circuitry. Let me illustrate this with some examples. Answer: Integrated operational amplifiers can perform various signal processing, such as filtering.oscilloscope, etc. 150. Integrated op amps can be used in almost every aspect of analog circuitry. Let me illustrate this with some examples. Answer: The integrated operational amplifier can realize different AC and DC amplification. 151. Integrated op amps can be used in almost every aspect of analog circuits. Let me illustrate this with some examples. Answer: An integrated operational amplifier can be used to generate sine waves and implement various waveform transformations. 152. The circuit is shown in Figure 1, and expression uo is written. Answer: uo=(1+RF/R1)ui 153. The circuit is shown in Figure 2, write down expression uo. Answer: uo=-(Rf/R1) ui 154. What is DC balance of an integrated op-amp? Answer: When DC resistance of two input terminals of an integrated op-amp is same with respect to ground, integrated op-amp is said to be in DC symmetrical state. When an integrated op amp is used, it must always match DC balance. 155. What are characteristics of connection between circuit stage and stage formed by integrated operational amplifier? Answer: Since input impedance Rid of built-in op-amp is very large and output impedance Rod is very low, it is easy to implement inter-stage coupling. 156. What is a sine wave generator? Answer: A circuit that can automatically generate a sine wave is called a sine wave generator. 157. What are two main types of sine wave generators in this course? Answer: The sine generators in this course mainly include RC sine generators and LC sine generators. 158. What are main components of a sine wave generator? Answer: A sine wave oscillator is mainly composed of an amplifier in an amplified state, a frequency selection network, and a feedback network. 159. What are conditions for generating blueusoidal vibrations? Answer: The condition for generating sinusoidal oscillations: (1) Satisfying shock condition when starting vibration: AF＞1φa+φf＝2nπ (2) Satisfying equilibrium condition after balancing: AF＝1φa+φf＝2nπ 160. What are structural characteristics of an RC sine wave oscillator? Answer: The frequency selection circuit and feedback circuit of an RC sine wave generator consist of RC components. 161. What are characteristics of frequency generated by RC sine wave generator? Answer: The oscillation frequency of an RC sinusoidal generator is usually . RC sine wave generators are easy to generate low frequency sine waves, but not easy to generate high frequency sine waves. 162. What are specifications of RC sine wave oscillator amplifier? Answer: Since RC sine wave generator easily generates low frequency sine waves, amplifier of RC sine wave generator can be composed of an integrated operational amplifier and a discrete amplifier. 163. What are structural characteristics of an LC sine wave oscillator? Answer: The frequency selection circuit and feedback circuit of an LC sine wave generator consist of LC components. 164. What are characteristics of frequency produced by an LC sine wave generator? Answer: The oscillation frequency of an LC-sinusoidal generator is usually equal to . LC sine wave generators are easy to generate high frequency sine waves, but not easy to generate low frequency sine waves. 165. What are characteristics of LC sine wave oscillator amplifier? Answer: Since LC sine wave generator easily generates high frequency sine waves, amplifier of LC sine wave generator can only consist of discrete amplifiers. 166. In this course, what are main types of LC sine wave generators? Answer: The LC sine generators in this course mainly include transformer feedback sine generators, inductive three-point sine generators, and capacitor three-point sine generators. 167. Which element of a crystal oscillator is equivalent to a sine wave oscillator? Answer: When operating frequency is between fp and fs, crystal oscillator is equivalent to an inductive element, and when operating frequency is fs, crystal oscillator is equivalent to a resistive element. 168. What is a parallel crystal oscillator circuit? Answer: When operating frequency is between fp and fs, quartz crystal works in a parallel resonant state, which is equivalent to an inductor. At present, a sine wave oscillator (usually an LC sine wave oscillator) consisting of it and other components in a circuit is referred to as a parallel quartz crystal oscillator circuit. 169. What is a series crystal oscillator circuit? Answer: At operating frequency fs, quartz crystal worksit is in series resonance state, which is equivalent to a resistive element. At present, a sine wave oscillator formed as a feedback path element in a circuit is called a series crystal oscillator circuit. It can be an RC sine generator or an LC sine generator. 170. What kind of feedback is introduced into sinusoidal generator? Answer: Positive feedback is introduced into sinusoidal generator. 171. What is a filter? Answer: A filter is a circuit that can pass useful frequency signals and suppress unwanted frequency components. 172. What is a passive filter? Answer: A filter consisting of passive components R, C, L, etc. is called a passive filter. 173. What is an active filter? Answer: A filter consisting of passive components R, C and an integrated operational amplifier of an active device is called an active filter. 174. What is an LPF Low Pass Filter? Answer: The LPF is a circuit that can pass low frequency signals, but does not pass high frequency signals. 175. What is upper cutoff frequency fH of LPF? Answer: As Auf of low pass filter is increased, LPF drops to 0.707 (-3dB) of corresponding frequency. 176. What is an HPF High Pass Filter? Answer: The HPF is a circuit that can pass high frequency signals but does not pass low frequency signals. 177. What is low cutoff frequency fL of HPF high pass filter? Answer: When HPF gain Auf drops to 0.707 (-3 dB), corresponding frequency. 178. What is a BPF Bandpass Filter? Answer: The BPF is a circuit that can pass signals within a certain frequency band, but cannot pass signals beyond it. 179. What are upper cutoff frequency fH and lower cutoff frequency fL of BPF? Answer: When gain Auf of bandpass filter BPF drops to 0.707 (-3 dB), corresponding frequency. There are currently two, namely upper cutoff frequency limit fH and lower cutoff frequency limit fL. 180. What is a BEF notch filter? Answer: A BEF notch filter is a circuit that cannot pass signals within a certain frequency band, but can pass signals outside of it. 181. What is an all-pass ACE filter? Answer: An all-pass ACE filter is a circuit that has same Auf (phase shift can be different) for all frequencies. 182. What is passband and stopband of a filter? Answer: The frequency band that filter passes is called passband, and frequency band that is not passed is called stopband. 183. What is characteristic frequency f0 of filter? Answer: The characteristic frequency f0 of filter is a constant with a frequency dimension determined by circuit. 184. What is quality factor Q of a filter? Answer: The quality factor of filter Q is a constant describing transient characteristics of filter. 185. What are characteristics of filter at Q=0.707? Answer: The filter at Q=0.707 has a flat transient response, and cutoff frequency is numerically equal to characteristic frequency. 186. What is a DC power supply? Answer: A DC power supply is a circuit that converts alternating current into stable direct current. 187. What are components of a DC power supply? Answer: A DC power supply consists of three parts: rectification, filtering, and voltage stabilization. 188. What is main function of a rectifier? Answer: The main function of a rectifier is to convert an AC voltage into a pulsating DC voltage. 189. What components are mainly used for rectification? Answer: In rectification, rectifier diodes are mainly used, which are implemented due to their one-sided conduction. 190. What is most commonly used rectifier circuit? Answer: The most commonly used rectifier circuit is bridge rectifier circuit. 191. What is main function of filtering? Answer: The main function of filtering is to remove AC component in ripple voltage and turn it into a smooth DC voltage. 192. What is most important filtration component? Answer: The most important filtration componentAn important element is capacitive element. 193. What is main function of a voltage regulator? Answer: The main function of a voltage regulator is to maintain a stable output voltage. 194. What are main advantages of three-terminal voltage regulator? Answer: The three-terminal voltage regulator has only three output terminals, fewer external components in application, easy to use, stable performance and low price. 195. What are main types of three-pole regulators? Answer: There are two main types of three-pole regulators: fixed-displacement three-pole regulators and variable-displacement three-pole regulators. . 196. What components does a three-terminal voltage regulator consist of? Answer: A three-terminal voltage regulator consists of regulating tubes, measuring circuits, reference voltages and comparative amplifiers. 197. In what state does adjusting tube of three-pole voltage regulator work? Answer: The adjusting tube of three-pole voltage regulator works in expanded state. 198. What are main characteristics of switching regulated power supply? Answer: Regulating tube of switching regulated power supply pOperates in switching state, that is, in states of conduction and cutoff. . 199. What are main advantages of switching regulated power supply? Answer: Because control tube of switching regulated power supply operates in switch state, efficiency is high, up to 80%-90%, and has a large wide voltage regulation range. 200. What are main disadvantages of a switching regulated power supply? Answer: The main disadvantage of a switching regulated power supply is that output voltage contains relatively large ripples.
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