A typical differential amplifier circuit constructed with an op amp is subject to which limitations?

A typical differential amplifier circuit constructed with an op amp is subject to which limitations?

• A. Thermal drift only
• B. Slew rate limitations and bandwidth limitations
• C. Noise only
• D. Power supply fluctuations only

Answer: (B)

The key idea is the op-amp’s finite dynamic performance. A differential amplifier built with an op-amp cannot respond instantly to input changes. The speed at which the output can rise or fall is limited by the op-amp’s slew rate—the maximum dV/dt the output can achieve. If the input demands a fast, large change, the output clips or distorts because it can’t slew fast enough. Another fundamental limit is the amplifier’s bandwidth. An op-amp has a finite gain that falls with frequency, so the closed-loop gain of a differential amplifier can only be maintained up to a certain frequency. The higher the desired gain, the smaller the usable bandwidth (roughly governed by the gain–bandwidth product). Beyond that, the signal is attenuated and distorted. These two dynamic limits—how quickly the output can change and how much gain is preserved at frequency—set the primary constraints on the differential amplifier’s fidelity for fast or high-frequency signals. Thermal drift, noise, and power-supply fluctuations are real factors too, but they do not define the basic ability to accurately reproduce rapidly changing signals in the way slew rate and bandwidth do.

The key idea is the op-amp’s finite dynamic performance. A differential amplifier built with an op-amp cannot respond instantly to input changes. The speed at which the output can rise or fall is limited by the op-amp’s slew rate—the maximum dV/dt the output can achieve. If the input demands a fast, large change, the output clips or distorts because it can’t slew fast enough.

Another fundamental limit is the amplifier’s bandwidth. An op-amp has a finite gain that falls with frequency, so the closed-loop gain of a differential amplifier can only be maintained up to a certain frequency. The higher the desired gain, the smaller the usable bandwidth (roughly governed by the gain–bandwidth product). Beyond that, the signal is attenuated and distorted.

These two dynamic limits—how quickly the output can change and how much gain is preserved at frequency—set the primary constraints on the differential amplifier’s fidelity for fast or high-frequency signals. Thermal drift, noise, and power-supply fluctuations are real factors too, but they do not define the basic ability to accurately reproduce rapidly changing signals in the way slew rate and bandwidth do.