Real operational amplifiers (A-level only) Flashcards – AQA A-level Physics (7408)

What does an operational amplifier’s frequency response curve plot?

Voltage gain against input-signal frequency.

How does a real operational amplifier’s gain typically vary as frequency increases?

It remains approximately constant over a low-frequency range, then falls as frequency increases.

How is an operational amplifier’s upper cutoff frequency commonly defined?

The frequency at which gain falls to $1/\sqrt{2}$ of its low-frequency value, a decrease of $3\,\mathrm{dB}$.

For an amplifier response extending down to very low frequencies, what is the approximate bandwidth?

The frequency range from zero to the upper cutoff frequency.

What is the approximate gain–bandwidth relationship for a given operational amplifier?

$\text{gain} \times \text{bandwidth} = \text{constant}$

In an operational amplifier’s gain–bandwidth product, what does gain represent?

The magnitude of the closed-loop voltage gain in its approximately constant-gain region.

In an operational amplifier’s gain–bandwidth product, what does bandwidth represent?

The frequency range over which the gain is maintained, up to the cutoff.

How does changing the closed-loop gain affect an operational amplifier’s available bandwidth?

Increasing gain reduces bandwidth; reducing gain increases bandwidth.