How to determine whether an amplifier circuit is common collector or common emitter?
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How to determine whether an amplifier circuit is common collector or common emitter?

Posted Date: 2024-01-21

What is a common emitter amplifier circuit?

The common emitter amplifier circuit is a common triode amplifier circuit. It uses the emitter of the triode as the input terminal, the collector as the output terminal, and the base terminal is connected to a bias voltage through the input signal. In a common-emitter amplifier circuit, the input signal controls the amplitude of the output signal by changing the base voltage of the transistor.

In a common-emitter amplifier circuit, when the amplitude of the input signal increases, the base voltage of the transistor will increase accordingly. This results in an increase in the transistor emitter current, thereby increasing the amplitude of the output signal. Therefore, the common-emitter amplifier circuit can amplify the amplitude of the input signal.

A characteristic of the common-emitter amplifier circuit is that the phase difference between the output signal and the input signal is 180 degrees, that is, inversion amplification. In addition, since the emitter of the transistor is grounded, the input resistance of the common-emitter amplifier circuit is low and the output resistance is high.

Common emitter amplifier circuits are widely used in various electronic devices, such as audio amplifiers, radio frequency amplifiers, etc. It has good amplification performance and wide frequency response range, and is a commonly used amplification circuit topology.

How to determine whether an amplifier circuit is common collector or common emitter?

There are easy ways:

Observe the input and output ends of the signal, and look at the positive pole of the signal.

Common emitter circuit: The signal enters from the base and is taken out from the collector.

Common base circuit: The signal is input from the emitter and taken out from the collector.

Common collector circuit: The signal enters from the base and is taken out from the emitter.

DC operating point:

Resistor-capacitor coupling common emitter amplifier circuit (B-pole input, C-pole output)

Features:

The common-emitter amplifier circuit can amplify both current and voltage. The input and output are inverted; the output resistance is large and the frequency band is narrow.often used as low frequency

The unit circuit of the voltage amplifier circuit.

Basic common amplifier circuit (emitter output device, B-pole input, E-pole output)

The difference between common emitter amplifier circuit and common base amplifier circuit

Common-emitter amplifier circuit and common-base amplifier circuit are two common transistor amplifier circuit topologies. They have different characteristics in terms of input and output characteristics, input and output impedance, etc.

Common emitter amplifier circuit:

- The input signal is connected to the emitter of the triode and the output signal is taken from the collector of the triode.

-Higher amplification and larger voltage gain.

- The input resistance is lower and the output resistance is higher.

- Perform inverting amplification, and the output signal has the opposite phase to the input signal (180-degree phase difference).

- Can provide higher current amplification capability.

Common base amplifier circuit:

- The input signal is connected to the base of the triode and the output signal is taken from the emitter of the triode.

- Lower amplification, with smaller voltage gain.

- The input resistance is higher and the output resistance is lower.

- Perform positive-phase amplification, and the output signal has the same phase as the input signal.

- Can provide higher voltage amplification capability.

Because common-base amplifier circuits have high input impedance and low output impedance, they are often used as signal conditioning and matching circuits to match the impedance of the input signal to subsequent circuits. Common-emitter amplifier circuits are often used in situations that require larger current amplification and higher voltage gain, such as audio amplifiers and power amplifiers.

Review Editor: Huang Fei


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