Advanced techniques tackle advanced op amps' extremely low distortion

Operational amplifier (op-amp) distortion in complex designs can be measured through selective amplification, which moderates rather than negates the limitations of signal generators and signal analyzers. Selective amplification separates distortion and test signals and makes the amplifier distortion signal dominant in the measurement, although it also reduces measurement bandwidth. The selective-amplification technique is demonstrated using a voltage-follower connection as an example. Making the op amp part of the measurement system causes the amplifier's bandwidth to limit resolution of higher-order distortion harmonics. Selective amplification and signal separation both work in inverting circuits, but the combination makes more demands on measurement bandwidth. The advantages of power-supply bootstrapping and selective amplification in specific circuit designs are described.
The second Part of this 2-part series describes bow to measure the distortion of more complex amplifier circuits and bow to handle the highest-performance op amps. Selective amplification offers an [...]