Which of the following is NOT correct for a voltage-series feedback amplifier?

Explanation:

When analyzing the given statement and options related to voltage-series feedback amplifiers, it's essential to understand the fundamental concepts and characteristics of these amplifiers. The correct option here is the one that is NOT true for a voltage-series feedback amplifier.

Voltage-Series Feedback Amplifier:

A voltage-series feedback amplifier is a type of feedback amplifier where the feedback signal is derived from the output voltage and fed back in series with the input signal. This configuration is widely used in various electronic circuits, particularly in operational amplifiers (op-amps).

Characteristics:

• Input Impedance: One of the primary characteristics of a voltage-series feedback amplifier is that it increases the input impedance. This is because the feedback opposes any changes in the input voltage, making the amplifier appear as if it has a higher input impedance.
• Output Impedance: The output impedance of a voltage-series feedback amplifier is decreased. The feedback mechanism helps stabilize the output voltage, making it less dependent on the load and thereby reducing the output impedance.
• Gain Stability: The feedback in these amplifiers helps in stabilizing the gain, making the amplifier less sensitive to variations in the components or external conditions.

Let's analyze the given options to identify the incorrect statement:

Option 1: Also known as a transconductance amplifier.

A transconductance amplifier is an amplifier that converts an input voltage to an output current. This is not characteristic of a voltage-series feedback amplifier, which is designed to amplify voltage. Therefore, this statement is NOT correct for a voltage-series feedback amplifier.

Option 2: Increases input impedance and decreases output impedance.

This is a correct statement for a voltage-series feedback amplifier. The feedback mechanism increases the input impedance and decreases the output impedance, as explained above.

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

This is also a correct statement. A non-inverting op-amp uses voltage-series feedback to stabilize the gain and improve performance.

Option 4: Also known as a voltage-controlled voltage source.

This is a correct statement. A voltage-series feedback amplifier can be considered a voltage-controlled voltage source (VCVS) because it amplifies the input voltage to produce a proportional output voltage.