Amplifier Performance Ratings

Amplifier Performance Ratings

Main factors that affect the performance of an amplifier are

1.       Stability

2.       Speed of response (bandwidth, slew rate)

3.       Unmolded signals

in which

K=gain of the differential amplifier (i.e., differential gain)

ucm=common-mode voltage (i.e., voltage common to both input leads)

uocm=common-mode output voltage (i.e., output voltage due to common-mode input voltage)

Note that ideally uocm=0 and CMRR should be infinity. It follows that the larger the CMRR the better the differential amplifier performance.

The three types of unmolded signals mentioned above can be considered as noise. In addition, there are other types of noise signals that degrade the performance of an amplifier.

 For example, ground-loop noise can enter the output signal. Furthermore, stray capacitances and other types of unmodeled circuit effects can generate internal noise.

 Usually in amplifier analysis, unmodeled signals (including noise) can be represented by a noise voltage source at one of the input leads.

 Effects of unmodeled signals can be reduced by using suitably connected compensating circuitry including variable resistors that can be adjusted to eliminate the effect of unmodeled signals at the amplifier output.