Knowing and remembering some basic analog circuits is a must for an electronic person, such as which components in the circuit play a key role, which component fails to affect the function of the circuit, and even the flow of circuit signals, the phase Changes, etc., also need to be understood and mastered.

Analog circuits refer to circuits used to transmit, transform, process, amplify, measure and display analog signals. An analog signal refers to a continuously changing electrical signal. Analog circuit is the basis of electronic circuit, which mainly includes amplifier circuit, signal operation and processing circuit, oscillation circuit, modulation and demodulation circuit and power supply. Next, share some common problems of analog circuits.

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1. What is zero drift? How to suppress zero drift?

Answer: Zero drift means that when the input end of the amplifier circuit is short-circuited, there is still a slowly changing voltage at the output end, that is, the output voltage deviates from the original starting point and drifts up and down.

2. What are the most important physical properties of a PN junction?

A: One-way conductivity and more sensitive temperature characteristics.

3. Is the terminal voltage and current applied to the PN junction linear? Why does it have unidirectional conductivity?

Answer: It is not linear. When the 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, resulting in a recombination phenomenon, which leads to the thinning of the barrier layer, and the forward current increases with the voltage. The growth increases exponentially, showing a macroscopically on state, and when the reverse voltage is added, the situation is just the opposite, the barrier layer becomes thicker, the current is almost completely zero, and the macroscopically shows a cut-off state. This is the unidirectional conduction characteristic of the PN junction.

4. Why should feedback be introduced into the circuit?

Answer: The purpose of introducing feedback DC negative feedback in the circuit is to stabilize the static operating point; the purpose of introducing AC negative feedback is to stabilize the magnification, change the input resistance and output resistance, expand the frequency band, and reduce nonlinear distortion.

5. What is the difference between the requirements of the voltage amplifier circuit and the power amplifier circuit?

Answer: The voltage amplifier circuit is mainly to amplify the signal without distortion, which requires a higher voltage or current amplification and appropriate input and output resistances. The power amplifier circuit mainly requires the highest possible output power and efficiency.