# FET Amplifier Impedance

• MHR-Love
In summary, FET Amplifier Impedance is the total resistance that an FET amplifier presents to an input signal. It is calculated by dividing the output voltage by the input current and the output voltage by the output current. FET Amplifier Impedance is important because it affects the performance of the amplifier and can be influenced by factors such as the type of FET, circuit design, and external components. It also has an impact on the frequency response of the amplifier.
MHR-Love
Hi guys,
can anyone tell me the reason why we set Vi=0 (short circuit the input side) when we want to find the output impedance Zo but we don't do the same by setting Vo=0 when we find the input impedance Zi?
and why do we let Io=0 (open circuit the output side) to find the gain Av?

thank you

Think of what is happening in the FET from the point of view of impedance. The collector-emitter side can be viewed as a current source. What are the implications of this?

## 1. What is FET Amplifier Impedance?

FET (Field Effect Transistor) Amplifier Impedance refers to the total resistance that an FET amplifier presents to an input signal. It is a measure of how much the amplifier will alter the input signal as it passes through it.

## 2. How is FET Amplifier Impedance calculated?

FET Amplifier Impedance can be calculated by dividing the output voltage of the amplifier by the input current. This is known as the input impedance. The output impedance can be calculated by dividing the output voltage by the output current.

## 3. Why is FET Amplifier Impedance important?

FET Amplifier Impedance is important because it affects the performance of the amplifier. A high impedance can cause signal loss and distortion, while a low impedance can cause excessive power consumption and reduced stability.

## 4. How does FET Amplifier Impedance affect frequency response?

FET Amplifier Impedance affects frequency response by causing a change in the amplitude and phase of the input signal at different frequencies. This can result in a non-uniform response and affect the overall performance of the amplifier.

## 5. What factors can affect the FET Amplifier Impedance?

FET Amplifier Impedance can be affected by various factors such as the type and characteristics of the FET used, the circuit design, and the external components connected to the amplifier. Temperature, biasing, and aging can also have an impact on the impedance of the amplifier.

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