An ideal op-amp in a voltage follower circuit has

An ideal op-amp in a voltage follower circuit has

• A. Nonlinear transfer function.
• B. Finite input impedance.
• C. Finite output impedance.
• D. Infinite input impedance and zero output impedance.

Answer: (D)

In a voltage follower, the op-amp is used with negative feedback to make the output voltage match the input voltage. The defining properties of an ideal op-amp are that it draws no input current (infinite input impedance) and its output can drive any load without a resistive voltage drop (zero output impedance). Together, these ensure the source is not loaded (no current drawn from the input) and the output voltage stays equal to the input even when a load is connected. If the op-amp had finite input impedance, the source would be loaded and the signal could be distorted; if it had finite output impedance, the voltage at the output would drop when driving a load. So the best description for an ideal op-amp in a voltage follower is infinite input impedance and zero output impedance.

In a voltage follower, the op-amp is used with negative feedback to make the output voltage match the input voltage. The defining properties of an ideal op-amp are that it draws no input current (infinite input impedance) and its output can drive any load without a resistive voltage drop (zero output impedance). Together, these ensure the source is not loaded (no current drawn from the input) and the output voltage stays equal to the input even when a load is connected. If the op-amp had finite input impedance, the source would be loaded and the signal could be distorted; if it had finite output impedance, the voltage at the output would drop when driving a load. So the best description for an ideal op-amp in a voltage follower is infinite input impedance and zero output impedance.