# How to calculate output voltage for ac coupled inverting amplifier

#### sharimin

Dec 17, 2013
8
How to calculate the output voltage for this ac coupled inverting amplifier

#### duke37

Jan 9, 2011
5,364
The gain of a virtual earth amplifier is just output resistance divided by the input resistance, in this case 40000/56 = 714.

There are two things to be considered;-
1. The operational amplifier must have a gain much higher than this.
2. The input capacitor will provide a significant impedance and lower gain at lower frequencies. I suggest you put this circuit into a simulation program to se the effect.

#### mursal

Dec 13, 2013
75
The voltage divider R3, R4 gives a bias voltage of 2Volts on the non inverting input. So the AC waveform will swing + and - on this bias voltage.
Vout = (-R2/R1)Vin + Vbias
Its a while since I covered this material, so hold tight until someone else has a look, I'm probably missing something.

#### sharimin

Dec 17, 2013
8
from simulation : if the input is 10.603V, the output is 2.377KV..

but, i want to know how the calculation and the formula..

pls help me..

#### mursal

Dec 13, 2013
75
Its a small signal amplifier (low voltage) try this link Click

#### duke37

Jan 9, 2011
5,364
mursal has given the formula, you should be able to evaluate that.

The op-amp cannot provide more voltage than its power supply voltage so 2.337kV (not 2.337KV !) is absurd. With an output swing of 1V, the maximum signal input would be 1/714 = 1.4mV

#### sharimin

Dec 17, 2013
8
so this circuit is wrong??

thank you for the information, i will try with the new circuit.

#### (*steve*)

##### ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,507
Well, it's wrong in that you'll never get 2.33kV (nor will any simple op-amp circuit)

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