amplifier open loop gain measure

[samtsui]

Hi
How to measure the open loop gain of an amplifier using the gain-phase analysis? Since the output signal of the gain-phase analysis is large 126uV, if the amplifier have 120dB gain, the output of the amp will be saturated. So have any technique to measure the gain-phase in open loop gain?

 

[surianova]

Hi
How to measure the open loop gain of an amplifier using the gain-phase analysis? Since the output signal of the gain-phase analysis is large 126uV, if the amplifier have 120dB gain, the output of the amp will be saturated. So have any technique to measure the gain-phase in open loop gain?

If it is diff amp, put DC voltage at both input ( make sure that DC voltage is the common mode range voltage for this diff amp). And put ac=1 at one of the input.
Then measure out to in, the gain and the phase.

For transient, if the gain is too high, choose very small input, so that output still in the saturation.


Surianova