frankrose
Advanced Member level 3
Hi!
I wanted to calculate a buffer's open loop DC gain when the loop is closed. I added an AC voltage source (magnitude=1V, freq=0.1Hz) in series with a 1.2V DC source, and I calculated the voltage difference between the two inputs of the buffer at 0.1Hz:
LoopGain = 1 / (mag(value(VF("/Vin_plus") 0.1)) - mag(value(VF("/Vin_minus") 0.1)))
Over PVT corners I got back the same value as in stb analysis at 0.1Hz, but with Monte Carlo (only mismatch) the denominator's sign sometimes negative, because the feedback voltage magnitude is higher than on the other input.
Why? AC offset? The feedback voltage always should be lower than the voltage on the other input, or what did I wrong? Thanks.
I wanted to calculate a buffer's open loop DC gain when the loop is closed. I added an AC voltage source (magnitude=1V, freq=0.1Hz) in series with a 1.2V DC source, and I calculated the voltage difference between the two inputs of the buffer at 0.1Hz:
LoopGain = 1 / (mag(value(VF("/Vin_plus") 0.1)) - mag(value(VF("/Vin_minus") 0.1)))
Over PVT corners I got back the same value as in stb analysis at 0.1Hz, but with Monte Carlo (only mismatch) the denominator's sign sometimes negative, because the feedback voltage magnitude is higher than on the other input.
Why? AC offset? The feedback voltage always should be lower than the voltage on the other input, or what did I wrong? Thanks.