Which of the following options is INCORRECT for a voltage-shunt feedback amplifier?

A voltage-shunt feedback amplifier, also known as a transresistance amplifier, is a type of feedback amplifier where the feedback network samples the output voltage and feeds back a current to the input. This type of feedback amplifier is widely used in various applications because it stabilizes the gain, reduces distortion, and improves the bandwidth of the circuit.

Key Features of Voltage-Shunt Feedback Amplifiers:

• The feedback network is connected in parallel with both the input and output of the amplifier.
• The input impedance of the amplifier is reduced due to the parallel connection of the feedback network.
• The output impedance is also reduced, making it suitable for driving low-impedance loads.
• These amplifiers are commonly used in applications requiring low output impedance and high stability, such as current-to-voltage converters and transimpedance amplifiers.

Correct Option Analysis:

The correct option is:

Option 3: A non-inverting op-amp is an example of a voltage-shunt feedback amplifier.

This option is incorrect because a non-inverting op-amp does not use a voltage-shunt feedback mechanism. In a non-inverting op-amp configuration, the feedback is voltage-series, meaning that the output voltage is fed back to the input in series with the input signal. This type of feedback increases the input impedance of the amplifier and stabilizes the voltage gain but does not involve the shunt feedback mechanism characteristic of voltage-shunt feedback amplifiers.

Important Information

To further understand the analysis, let’s evaluate the other options:

Option 1: An inverting operational amplifier uses a voltage-shunt feedback mechanism.

This option is correct. In an inverting op-amp configuration, the feedback network connects the output to the inverting input in parallel, creating a shunt feedback mechanism. The output voltage is sampled, and the feedback current flows back to the input, stabilizing the circuit's gain and improving its performance.

Option 2: A collector-base bias circuit is an example of a voltage-shunt feedback amplifier.

This option is correct. A collector-base bias circuit in a transistor amplifier uses a voltage-shunt feedback mechanism. The feedback is applied by connecting the collector to the base through a resistor. This configuration stabilizes the operating point of the transistor by providing negative feedback.

Option 4: It is also known as a transresistance amplifier.

This option is correct. A voltage-shunt feedback amplifier is indeed referred to as a transresistance amplifier because its output is a voltage, and its input is a current. The gain of such an amplifier is expressed in terms of resistance (volts per ampere).