A common gate amplifier hasa)high input resistance and high output res...
FET:
As the input circuit of FET is reverse biased, FET exhibits a much higher input impedance ( in the order of 100 M 12 ) and lower output impedance and there will be a high degree of isolation between input and output.
So, FET can act as an excellent buffer amplifier but the BJT has low input impedance because its input circuit is forward biased.
A common gate amplifier hasa)high input resistance and high output res...
Common Gate Amplifier
A common gate amplifier is a type of field-effect transistor (FET) amplifier configuration. It is commonly used in electronic circuits to amplify and shape electrical signals. In this configuration, the input signal is applied to the gate terminal of the FET, the output is taken from the source terminal, and the drain terminal is biased.
Input Resistance
The input resistance of an amplifier is a measure of how much the amplifier circuit affects the source of the input signal. It is defined as the ratio of the change in input voltage to the change in input current. A high input resistance means that the amplifier draws very little current from the source, allowing the source to deliver the signal without distortion.
Output Resistance
The output resistance of an amplifier is a measure of how much the amplifier circuit affects the load connected to its output. It is defined as the ratio of the change in output voltage to the change in output current. A high output resistance means that the amplifier can deliver a voltage signal with minimal distortion to the load.
Characteristics of a Common Gate Amplifier
The common gate amplifier configuration has the following characteristics:
1. Low Input Resistance: The input resistance of a common gate amplifier is typically low. This is because the input signal is applied to the gate terminal, which acts as a forward-biased diode. As a result, the input current is high, leading to a low input resistance.
2. High Output Resistance: The output resistance of a common gate amplifier is typically high. This is because the output signal is taken from the source terminal, which is connected to the bulk of the FET. The source terminal has a high resistance to the flow of current, resulting in a high output resistance.
Advantages and Applications
The common gate amplifier configuration offers several advantages, including:
1. High voltage gain
2. Good frequency response
3. Low noise
These advantages make it suitable for applications such as RF amplifiers, mixers, and frequency converters.
Conclusion
In conclusion, a common gate amplifier has a low input resistance and a high output resistance. This configuration allows for high voltage gain, good frequency response, and low noise. It is commonly used in RF applications where these characteristics are desirable.
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