Question
What is the gain-bandwidth of an operational amplifier?
Answer Options
- A) The maximum frequency for a filter circuit using that type of amplifier
- B) The frequency at which the open-loop gain of the amplifier equals one
- C) The gain of the amplifier at a filter’s cutoff frequency
- D) The frequency at which the amplifier’s offset voltage is zero
Correct Answer: B
Explanation
The gain-bandwidth product (\text{GBW} or \text{GBWP}) is a critical specification for an operational amplifier. It is a figure of merit that quantifies the compromise between voltage gain and operating frequency, as the open-loop gain of an \text{op-amp} is intentionally designed to roll off quickly with increasing frequency to ensure stability.
An \text{op-amp}'s gain-bandwidth is defined as the frequency at which the open-loop gain of the amplifier equals one (unity), or 0 \text{ dB}. This metric is useful because it allows a designer to quickly determine the maximum achievable closed-loop gain for a given operating frequency: Gain_{CL} = \text{GBWP} / F. For example, an \text{op-amp} with a 10 \text{ MHz} \text{GBWP} can provide a stable gain of 10 at 1 \text{ MHz}.
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