I heard that those who read these two hundred questions carefully all succeeded in the interview.[Copy link]
1. What are the characteristics of electronic devices made of semiconductor materials compared with traditional vacuum electronic devices? Answer: Good frequency characteristics, small size, low power consumption, convenient for the miniaturization of integrated circuit products, and also particularly outstanding in terms of ruggedness, earthquake resistance and reliability; but not as good as vacuum devices in terms of distortion and stability. 2. What are intrinsic semiconductors and impurity semiconductors? Answer: Pure semiconductors are intrinsic semiconductors, and they are generally medium-valent elements in the periodic table. Impurity semiconductors are obtained after adding high-valent or low-valent impurity elements to intrinsic semiconductors in a very small proportion. 3. Are holes a type of carrier? Do electrons move when holes conduct electricity? Answer: No, but they can be equivalent to carriers in their movement. When holes conduct electricity, electrons of equal electric charge will move in the opposite direction. 4. When preparing impurity semiconductors, what proportion is generally used to dope intrinsic semiconductors? Answer: It is doped at a ratio of one millionth of the order of magnitude. 5. What is an N-type semiconductor? What is a P-type semiconductor? What phenomenon will occur when the two semiconductors are made together? Answer: Semiconductors whose majority carriers are free electrons are called N-type semiconductors. On the contrary, semiconductors whose majority carriers are holes are called P-type semiconductors. When a P-type semiconductor is joined with an N-type semiconductor, a PN junction is formed. 6. What are the main physical properties of a PN junction? Answer: Unidirectional conductivity and relatively sensitive temperature characteristics. 7. What other names are there for a PN junction? Answer: Space charge region, barrier layer, depletion layer, etc. 8. Is the voltage and current applied to a PN junction linear? Why does it have unidirectional conductivity? Answer: It is not linear. When a forward voltage is applied, the holes in the P region and the electrons in the N region attract each other under the electric field established by the forward voltage to produce a recombination phenomenon, causing the barrier layer to become thinner. The forward current increases exponentially with the increase in voltage, and it is in a conducting state on a macroscopic scale. When a reverse voltage is applied, the situation is exactly the opposite of the above. The barrier layer becomes thicker, the current is almost completely zero, and it is in a cut-off state on a macroscopic scale. This is the unidirectional conductive characteristic of a PN junction. 9. Is there really no current when a reverse voltage is applied to a PN junction? Answer: It is not that there is no current at all. Minority carriers produce a very small reverse leakage current under the action of a reverse voltage. 10. What are the most basic technical parameters of a diode? Answer: Maximum rectified current 11. What are the main uses of a diode? Answer: Rectification, detection, voltage regulation, etc. 12. How does a transistor control the collector current? Answer: Through the current distribution relationship. 13. Can two diodes connected inversely to form a triode? Why? Answer: No; two diodes connected inversely to each other are connected through metal electrodes, and do not form the base region required for a triode. 14. What is the penetration current of a triode? What effect does it have on the amplifier? Answer: When the base is open, the current between the collector and the emitter is the penetration current: , where is the collector-base reverse leakage current, and are both generated by the movement of minority carriers, so they are very sensitive to temperature. When the temperature rises, both will increase sharply. This will have an adverse effect on the amplifier. Therefore, in actual work, they are required to be as small as possible. 15. What is the gate voltage of a triode? Answer: Silicon tubes are generally 0.5 volts. Germanium tubes are about 0.2 volts. 16. Does the amplifier circuit amplify electrical signals in the same sense as a magnifying glass amplifying an object? Answer: Not the same. 17. In an amplifier composed of triodes, what are the basic bias conditions? Answer: The emitter junction is forward biased; the collector junction is reverse biased. 18. What are the regions of the input and output characteristic curve of a triode? Answer: Generally divided into amplification region, saturation region and cut-off region. 19. How many basic configurations are there for amplifier circuits? What are they? Answer: There are three types, namely common emitter, common base and common collector. 20. In a common emitter amplifier circuit, what are the general bias circuits? Answer: There are upper base bias, voltage divider and collector-base feedback. 21. What is the significance of determining the static operating point for the amplifier? Answer: Correctly determining the static operating point can make the amplifier have the smallest cut-off distortion and saturation distortion, and at the same time can obtain the largest dynamic range and improve the efficiency of the triode. 22. In what region of the input and output characteristic curve of the triode should the static operating point of the amplifier generally be? Answer: It should usually be in the center of the amplification area of the input-output characteristic curve of the transistor. 23. When drawing the DC path of the amplifier, how should the power supply and capacitor be treated? Answer: The capacitor should be regarded as an open circuit, and the power supply as an ideal power supply. 24. Which amplifiers are suitable for the graphical method of amplifiers? Answer: It is generally suitable for common-emitter base-biased single-tube amplifiers and push-pull power amplifiers. 25. What are the significances of the DC load line and AC load line in the graphical method of amplifiers? Answer: The DC load line determines the DC path parameters in static state. The significance of the AC load line is to analyze the maximum effective amplitude and waveform distortion of the amplifier output when there is an AC signal. 26. How to evaluate the performance of the amplifier circuit? What are the main indicators? Answer: The performance of the amplifier circuit is generally determined by the following indicators: gain, input and output resistance, passband, distortion, and signal-to-noise ratio. 27. Why is the unit of the voltage gain of the amplifier often decibel? What is the relationship between it and the multiple? Answer: The unit of the voltage gain of the amplifier is often decibel because of the following reasons: (1) The value becomes smaller and is easy to read and write. (2) It is easy to calculate. (3) It is in line with the sense of hearing and easy to estimate. The relationship between the two is: 28. Is the passband of the amplifier as wide as possible? Why? Answer: No! The width of the amplifier passband is not the wider the better. The key is whether the amplifier has special requirements for the signal frequency it processes! For example, the frequency-selective amplifier requires a very narrow passband, while the passband of a general audio amplifier is relatively wide. 29. What is the impact of the input and output resistance of the amplifier on the amplifier? Answer: The input resistance of the amplifier should be as high as possible, so that the effective output of the input signal source can be increased and the effective signal consumed by the internal resistance of the signal source can be reduced to the minimum range. The output resistance should be as low as possible, so that the effective output signal ratio on the load can be increased. 30. When designing an amplifier, what is the principle for selecting the value of the input and output resistance? Answer: High input and low output. 31. How many categories are there for amplifier distortion? Answer: Single-tube AC small signal amplifiers generally have three types of distortion: saturation distortion, cutoff distortion and nonlinear distortion. Push-pull power amplifiers may also have crossover distortion. 32. What kind of distortion will be caused if the working point of the amplifier is too high? What if the working point is too low? Answer: Saturation distortion, cutoff distortion 33. What are the general causes of the nonlinear distortion of the amplifier? Answer: When the working point falls in the nonlinear area of the input characteristic curve and the minimum value of the input signal is not zero, it will cause nonlinear distortion. 34. What is the difference between the micro-variable equivalent circuit analysis method and the graphical method in the analysis of amplifiers? Answer: It can be more convenient and accurate to calculate the input and output resistance, voltage gain, etc. of the amplifier. The graphical method can more intuitively analyze whether the working point of the amplifier is set appropriately, whether it will produce what kind of distortion and dynamic range, etc. 35. What are the general steps for analyzing the amplifier circuit using the micro-variable equivalent circuit analysis method? Answer: 1) Calculate the Q point; 2) Calculate the transistor according to the formula. 3) Use the micro-variable equivalent circuit to draw the AC path of the amplifier. 4) According to 3) and the corresponding formula, calculate the input and output resistance, voltage gain, etc. of the amplifier.36. What is the scope of application of the micro-variable equivalent circuit analysis method? Answer: It is suitable for analyzing any simple or complex circuit. As long as the amplifier components in it basically work within the linear range. 37. What are the limitations of the micro-variable equivalent circuit analysis method? Answer: It can only solve the calculation problem of the AC component, and cannot be used to determine the Q point, nor can it be used to analyze nonlinear distortion and maximum output amplitude. 38. What are the main factors that affect the stability of the amplifier's operating point? Answer: Temperature drift of component parameters, power supply fluctuations, etc. 39. What method is generally used to stabilize the operating point in the common emitter amplifier circuit? Answer: Introduce current series negative feedback. 40. Why can't a single-tube amplifier circuit meet the requirements of multiple performance aspects? Answer: The amplification capacity is limited; in terms of input and output resistance, it cannot simultaneously take into account the good matching of the amplifier and the outside world. 41. What is the basic purpose of the coupling circuit? Answer: Let the useful AC signal pass smoothly between the front and rear amplifiers, and at the same time play a good isolation in static terms. 42. How many ways are there generally for inter-stage coupling in multi-stage amplifier circuits? Answer: Generally, there are several ways, such as RC coupling, transformer coupling, and direct coupling. 43. What is the total voltage gain of a multi-stage amplifier circuit? Answer: It is equal to the product of the gains of each stage. 44. What is the input and output resistance of a multi-stage amplifier circuit? Answer: It is equal to the input resistance of the first stage and the output resistance of the last stage respectively. 45. What are the special problems of a direct-coupled amplifier circuit? How to solve it? Answer: Zero drift is the biggest problem of a direct-coupled amplifier circuit. The most fundamental solution is to use a differential amplifier. 46. Why is a three-stage amplifier circuit the most common? Answer: Too few stages will result in insufficient amplification capacity, and too many stages will make it difficult to solve problems such as zero drift. 47. What is zero drift? What are the main causes of it? What is the most fundamental one? Answer: When the input signal of the amplifier is zero, its output end still has a phenomenon of slow and irregular output signals. The main reason for this phenomenon is that the parameters of circuit components fluctuate due to the influence of temperature, resulting in the instability of the Q point. In a multi-stage amplifier, due to the use of direct coupling, the fluctuation of the Q point will be transmitted and amplified step by step. 48. What is feedback? What is DC feedback and AC feedback? What is positive feedback and negative feedback? Answer: The phenomenon that the output signal is sent back to the input end through a certain path and reprocessed by the amplifier is called feedback. If the signal is DC, it is called DC feedback; if it is AC, it is called AC feedback. After the reprocessing, the final output of the amplifier is larger than before the introduction of feedback, which is called positive feedback. On the contrary, if the final output of the amplifier is smaller than before the introduction of feedback, it is called negative feedback. 49. Why do we need to introduce feedback? Answer: In general, it is to improve the performance of the amplifier. The introduction of positive feedback is to enhance the sensitivity of the amplifier to weak signals or increase the gain; and the introduction of negative feedback is to improve the gain stability and working point stability of the amplifier, reduce distortion, improve input and output resistance, widen the passband, etc. 50. What are the four configurations of AC negative feedback? Answer: They are current series, current parallel, voltage series, and voltage parallel. 51. What is the general expression of AC negative feedback amplifier circuit? Answer: . 52. What effect will the performance have after the introduction of current series negative feedback in the amplifier circuit? Answer: It can weaken the voltage gain, improve its gain stability, reduce distortion, increase input resistance, increase output resistance, etc. 53. What effect will the performance have after the introduction of voltage series negative feedback in the amplifier circuit? Answer: It can weaken the voltage gain, improve its gain stability, reduce distortion, reduce input resistance, reduce output resistance, etc. 54. What effect will the performance have after the introduction of current parallel negative feedback in the amplifier circuit? Answer: It can weaken the voltage gain, improve its gain stability, reduce distortion, reduce input resistance, increase low output resistance, etc. 55. What effect will the performance have after the introduction of voltage parallel negative feedback in the amplifier circuit? Answer: It can weaken the voltage gain, improve its gain stability, reduce distortion, reduce input resistance, reduce low output resistance, etc. 56. What is deep negative feedback? Under deep negative feedback conditions, how to estimate the gain? Answer: In the feedback amplifier, if 1, then the amplifier that meets this condition is called a deep negative feedback amplifier. At this time, the closed-loop gain of the amplifier is completely determined by the feedback coefficient. 57. Is the deeper the negative feedback, the better? What is self-oscillation? What kind of feedback amplifier circuit is prone to self-oscillation? How to eliminate self-oscillation? Answer: No. When the closed-loop gain of the negative feedback amplifier circuit is ＝0, it means that the circuit has an output when the input is 0, and the circuit is said to have self-oscillation. When the signal frequency enters the low-frequency or high-frequency band, due to the generation of additional phase shift, the negative feedback amplifier circuit is prone to self-oscillation. To eliminate self-oscillation, it is necessary to destroy the conditions for oscillation and change the frequency characteristics of AF. 58. Can only negative feedback be introduced into the amplifier circuit? Can the introduction of positive feedback into the amplifier circuit improve performance? Answer: No. Yes, such as the bootstrap circuit, while introducing negative feedback, introduce appropriate positive feedback to increase the input resistance. 59. What kind of configuration is the voltage follower amplifier? Can it amplify the input voltage signal? Answer: The voltage follower is a voltage series amplifier. It cannot amplify the input voltage signal. 60. What type of feedback amplifier is the voltage follower? Answer: The voltage follower is a voltage series feedback amplifier. 61. What is the main use of the voltage follower? Answer: The main use of the voltage follower: generally used in the input stage and output stage of a multi-stage amplifier circuit, and can also be connected to two circuits to act as a buffer. 62. What are the input and output characteristics of the voltage follower? Answer: The input and output characteristics of the voltage follower: high input resistance and low output resistance. 63. Generally speaking, how many categories are power amplifiers divided into? Answer: According to the different conduction angles of the transistors in the entire cycle, they can be divided into Class A, Class B, Class AB, Class C, and Class D. According to the different circuit structures, they can be divided into transformer coupling, no output transformer OTL, no output capacitor OCL, and bridge push-pull power amplifier circuit BTL. 64. What are the characteristics of Class A and Class B power amplifiers? Answer: The characteristics of Class A power amplifiers: the transistor is turned on during the entire cycle of the signal, with high power consumption and low distortion; the characteristics of Class B power amplifiers: the transistor is only turned on during half of the signal cycle, with low power consumption and high distortion. 65. Why does Class B power amplifier produce crossover distortion? How to overcome it? Answer: Because there is a turn-on voltage Uon between transistors b-e. When the input voltage value |ui|. 52. What kind of effect will the performance have after the introduction of current series negative feedback in the amplifier circuit? Answer: It can weaken the voltage gain, improve its gain stability, reduce distortion, increase input resistance, increase output resistance, etc. 53. What kind of effect will the performance have after the introduction of voltage series negative feedback in the amplifier circuit? Answer: It can weaken the voltage gain, improve its gain stability, reduce distortion, reduce input resistance, reduce output resistance, etc. 54. What kind of effect will the performance have after the introduction of current parallel negative feedback in the amplifier circuit? Answer: It can weaken the voltage gain, improve its gain stability, reduce distortion, reduce input resistance, increase low output resistance, etc. 55. What kind of effect will the performance have after the introduction of voltage parallel negative feedback in the amplifier circuit? Answer: It can weaken the voltage gain, improve its gain stability, reduce distortion, reduce input resistance, reduce low output resistance, etc. 56. What is deep negative feedback? Under deep negative feedback conditions, how to estimate the gain? Answer: In the feedback amplifier, if 1, then the amplifier that meets this condition is called a deep negative feedback amplifier. At this time, the closed-loop gain of the amplifier is completely determined by the feedback coefficient. 57. Is the deeper the negative feedback, the better? What is self-oscillation? What kind of feedback amplifier circuit is prone to self-oscillation? How to eliminate self-oscillation? Answer: No. When the closed-loop gain of the negative feedback amplifier circuit is ＝0, it means that the circuit has an output when the input is 0, and the circuit is said to have self-oscillation. When the signal frequency enters the low-frequency or high-frequency band, due to the generation of additional phase shift, the negative feedback amplifier circuit is prone to self-oscillation. To eliminate self-oscillation, it is necessary to destroy the conditions for oscillation and change the frequency characteristics of AF. 58. Can only negative feedback be introduced into the amplifier circuit? Can the introduction of positive feedback into the amplifier circuit improve performance? Answer: No. Yes, such as the bootstrap circuit, while introducing negative feedback, introduce appropriate positive feedback to increase the input resistance. 59. What kind of configuration is the voltage follower amplifier? Can it amplify the input voltage signal? Answer: The voltage follower is a voltage series amplifier. It cannot amplify the input voltage signal. 60. What type of feedback amplifier is the voltage follower? Answer: The voltage follower is a voltage series feedback amplifier. 61. What is the main use of the voltage follower? Answer: The main use of the voltage follower: generally used in the input stage and output stage of a multi-stage amplifier circuit, and can also be connected to two circuits to act as a buffer. 62. What are the input and output characteristics of the voltage follower? Answer: The input and output characteristics of the voltage follower: high input resistance and low output resistance. 63. Generally speaking, how many categories are power amplifiers divided into? Answer: According to the different conduction angles of the transistors in the entire cycle, they can be divided into Class A, Class B, Class AB, Class C, and Class D. According to the different circuit structures, they can be divided into transformer coupling, no output transformer OTL, no output capacitor OCL, and bridge push-pull power amplifier circuit BTL. 64. What are the characteristics of Class A and Class B power amplifiers? Answer: The characteristics of Class A power amplifiers: the transistor is turned on during the entire cycle of the signal, with high power consumption and low distortion; the characteristics of Class B power amplifiers: the transistor is only turned on during half of the signal cycle, with low power consumption and high distortion. 65. Why does Class B power amplifier produce crossover distortion? How to overcome it? Answer: Because there is a turn-on voltage Uon between transistors b-e. When the input voltage value |ui|. 52. What kind of effect will the performance have after the introduction of current series negative feedback in the amplifier circuit? Answer: It can weaken the voltage gain, improve its gain stability, reduce distortion, increase input resistance, increase output resistance, etc. 53. What kind of effect will the performance have after the introduction of voltage series negative feedback in the amplifier circuit? Answer: It can weaken the voltage gain, improve its gain stability, reduce distortion, reduce input resistance, reduce output resistance, etc. 54. What kind of effect will the performance have after the introduction of current parallel negative feedback in the amplifier circuit? Answer: It can weaken the voltage gain, improve its gain stability, reduce distortion, reduce input resistance, increase low output resistance, etc. 55. What kind of effect will the performance have after the introduction of voltage parallel negative feedback in the amplifier circuit? Answer: It can weaken the voltage gain, improve its gain stability, reduce distortion, reduce input resistance, reduce low output resistance, etc. 56. What is deep negative feedback? Under deep negative feedback conditions, how to estimate the gain? Answer: In the feedback amplifier, if 1, then the amplifier that meets this condition is called a deep negative feedback amplifier. At this time, the closed-loop gain of the amplifier is completely determined by the feedback coefficient. 57. Is the deeper the negative feedback, the better? What is self-oscillation? What kind of feedback amplifier circuit is prone to self-oscillation? How to eliminate self-oscillation? Answer: No. When the closed-loop gain of the negative feedback amplifier circuit is ＝0, it means that the circuit has an output when the input is 0, and the circuit is said to have self-oscillation. When the signal frequency enters the low-frequency or high-frequency band, due to the generation of additional phase shift, the negative feedback amplifier circuit is prone to self-oscillation. To eliminate self-oscillation, it is necessary to destroy the conditions for oscillation and change the frequency characteristics of AF. 58. Can only negative feedback be introduced into the amplifier circuit? Can the introduction of positive feedback into the amplifier circuit improve performance? Answer: No. Yes, such as the bootstrap circuit, while introducing negative feedback, introduce appropriate positive feedback to increase the input resistance. 59. What kind of configuration is the voltage follower amplifier? Can it amplify the input voltage signal? Answer: The voltage follower is a voltage series amplifier. It cannot amplify the input voltage signal. 60. What type of feedback amplifier is the voltage follower? Answer: The voltage follower is a voltage series feedback amplifier. 61. What is the main use of the voltage follower? Answer: The main use of the voltage follower: generally used in the input stage and output stage of a multi-stage amplifier circuit, and can also be connected to two circuits to act as a buffer. 62. What are the input and output characteristics of the voltage follower? Answer: The input and output characteristics of the voltage follower: high input resistance and low output resistance. 63. Generally speaking, how many categories are power amplifiers divided into? Answer: According to the different conduction angles of the transistors in the entire cycle, they can be divided into Class A, Class B, Class AB, Class C, and Class D. According to the different circuit structures, they can be divided into transformer coupling, no output transformer OTL, no output capacitor OCL, and bridge push-pull power amplifier circuit BTL. 64. What are the characteristics of Class A and Class B power amplifiers? Answer: The characteristics of Class A power amplifiers: the transistor is turned on during the entire cycle of the signal, with high power consumption and low distortion; the characteristics of Class B power amplifiers: the transistor is only turned on during half of the signal cycle, with low power consumption and high distortion. 65. Why does Class B power amplifier produce crossover distortion? How to overcome it? Answer: Because there is a turn-on voltage Uon between transistors b-e. When the input voltage value |ui|
I heard that those who read these two hundred questions carefully all succeeded in the interview.
提升卡
变色卡
千斤顶
京公网安备 11010802033920号
