A two stage amplifier is a type of electronic circuit that amplifies the input signal in two stages, using two separate amplifying devices. This allows for a higher overall gain and better performance compared to a single stage amplifier.
In a two stage amplifier, the input signal is first amplified by the first stage, which is typically a small-signal amplifier. The output of the first stage then serves as the input for the second stage, which is usually a power amplifier. The output of the second stage is the final amplified signal.
The input resistance of a two stage amplifier is the equivalent resistance that the amplifier presents to the input signal. It is typically a combination of the input resistance of the first stage and the input resistance of the second stage.
The input resistance of a two stage amplifier can be calculated by dividing the input voltage by the input current. It can also be calculated by dividing the voltage gain of the amplifier by the current gain.
The input resistance of a two stage amplifier is important because it determines the amount of current that is drawn from the input signal source. A higher input resistance means that the amplifier will draw less current from the input source, which can help prevent loading effects and maintain the integrity of the input signal.