The main performance indicators of the amplifier circuit

What are the main performance indicators of amplifier circuits?

Answer: The performance indicators of an amplifier circuit are the standards for its quality and determine its scope of application.

1. Input resistance
The size of the input resistance Ri determines the amplitude of the signal absorbed by the amplifier circuit from the signal source. For the amplifier circuit with voltage signal as input, that is, voltage amplification and mutual conductance amplification, the larger Ri is, the larger Vi at the input end of the amplifier circuit is; for the amplifier circuit with current signal as input, that is, current amplification and mutual resistance amplification, the smaller Ri is, the larger the current injected into the amplifier circuit and the input current Ii is.

2. Output resistance
The size of the output resistance Ro of the amplifier circuit determines its load carrying capacity. For amplifier circuits with voltage output, i.e. voltage amplification and mutual resistance amplification, the smaller Ro is, the smaller the effect of the change of the load resistance RL on the output voltage Vo is, and it is mostly used for pre-amplification and intermediate stage amplification of signals; for amplifier circuits with current output, i.e. current amplification and mutual conductance amplification, the larger Ro is in parallel with the controlled current source, the smaller the effect of the change of the load resistance RL on the output current Io is, and it is often used in the output stage of electronic systems.

3. Gain
The four amplifier circuits have different gains, such as voltage gain Av, current gain AI, mutual resistance gain AR and mutual conductance gain AG. They actually reflect the ability of the amplifier circuit to convert the power supply energy into signal energy under the control of the input signal.

4. Frequency response and bandwidth
The frequency response of an amplifier circuit refers to the steady-state response of the output that continuously changes with frequency when a sinusoidal signal is input.

5. Nonlinear distortion
Nonlinear distortion is caused by the nonlinear characteristics of the amplifier. Amplifiers include discrete devices (such as semiconductor triodes, etc.) and integrated circuit devices (such as integrated operational amplifiers, etc.).
In addition, there are some other indicators for circuits with different uses, such as maximum output power, efficiency, signal-to-noise ratio, anti-interference ability, etc.

Why is a sine wave signal generator with continuously variable frequency often used as the experimental and test signal source for amplifier circuits?
Answer: Any signal can be decomposed into the sum of many sine signals. It can be said that the sine signal is the most basic signal, so continuously variable sine signals are often used as experimental and test signal sources for amplifier circuits.