Why zero output impedance in an ideal op-amp?

• A. To minimize current drawn from the supply
• B. To increase the gain beyond its limit
• C. To require larger external components
• D. To preserve signal integrity when delivering power

Answer: (D)

Having zero output impedance means the amplifier’s output behaves like an ideal voltage source. The key idea is that the voltage at the output stays constant regardless of how much current the load draws (within the device’s limits). That stability is what preserves the signal’s shape and amplitude when power is delivered to the load. If the output had any finite impedance, the load current would cause a voltage drop across that internal impedance, so the actual load voltage would deviate from the intended output. In practice, this fidelity is crucial for accurate amplification, especially as loads change or during transient current demands. The other options don’t address this effect: minimizing supply current isn’t a direct consequence of zero output impedance, increasing gain isn’t tied to the output’s ability to drive varying loads, and requiring larger external components isn’t related to the output’s ability to maintain the signal under load.