Question

How to convert the ratio gain Av = vout / vin = -60 to dB

because it will come out with error when 20log(-Av) ....

Pls Help me to solve it

Answer 1

Hello, the gain of amplifier may be in +ve or in -ve. But, -ve sign indicates that the output signal is is anti phase with the corresponding input signal. And also, the value of 20log(-60) is practically does not exists. Hence you have to take the value of 20log(60) and apply 180 degree phase shift to the input signal so that you can get the required result.

For the inverting op amps, you may see that the voltage gain for it is -Rf/R1. But, -ve sign in that indicate that the output is in anti phase with the output. And -ve sign cannot be included for the dB calculations.