Op-Amp
Closed-loop characteristics, gain-bandwidth product, maximum voltage change rate (slew rate)
Parameters
1. What does the "virtual short" approximation rely on in an ideal op-amp?
A. Infinite open-loop gain — negative feedback forces the voltage difference between the two inputs toward zero
B. A physical short circuit wire between the inputs
C. The fact that output impedance is infinite
D. The fact that the amplifier needs no power supply
2. If the gain-bandwidth product (GBW) is constant, what happens to the closed-loop bandwidth if the gain is increased?
A. Bandwidth decreases proportionally — high gain means narrow bandwidth
B. Bandwidth increases along with gain
C. Bandwidth is independent of gain
D. GBW has no relation to bandwidth at all
3. What happens to the output signal when the required slew rate exceeds the device's maximum slew rate?
A. The sine wave distorts toward a triangular shape and amplitude is reduced — the output cannot keep up with the ideal change
B. The output disappears completely
C. The output becomes a more accurate sine wave
D. The amplifier is physically damaged
4. Why does a voltage follower (buffer) still need an op-amp, if its gain is only 1?
A. It converts a high-impedance source into a low-output-impedance signal, without loading effects
B. To actually increase the gain
C. To add noise
D. It is not needed at all — a plain wire is sufficient