# Gain of a Circuit !

Joined Feb 10, 2007
64
i'm wondering ,why does a gain of multistage circuit (multistage amplifier,Three Op-Amp IA,Band-Pass Filter using one or more gain stages)the outputs obtained under certain conditions get added while the GAIN gets MULTIPLIED ,why is it so ? pls help me out .
- Alok.

#### Papabravo

Joined Feb 24, 2006
16,792
Could it be because a circuit can do more than one thing at a time?

Joined Feb 10, 2007
64
Sir You may be correct but i don't find it a convincing reply ! do you ?

#### bloguetronica

Joined Apr 27, 2007
1,453
Normaly the gain of a circuit is the product of the gains of its amplifier stages. But if you define the gain in dB, then you have the sum of all gains in bB. Is that it?

Joined Feb 10, 2007
64
you are right but in that sense for finding the total Avt we perform the following ;
Avt=Av1*Av2*.....*Avn
Ultimately aren't we mulitplying it !

#### recca02

Joined Apr 2, 2007
1,214
by output do you mean o/p of individual ckts are added?

Joined Feb 10, 2007
64
no output of individual circuits are not added i mean that the o/p is collective addtion at the last stage
For ex : In Case of a 3Op-amp IA before the difference amplifier stage i.e input to difference amplifier is V02-Vo1

#### recca02

Joined Apr 2, 2007
1,214
my experience with electronic circuits is limited ,wud it be possible for you to post a rough schematic of above mentioned config ,i wud like to analyse it if i can.

#### Papabravo

Joined Feb 24, 2006
16,792
Sir You may be correct but i don't find it a convincing reply ! do you ?
OK - would you be more convinced if I said that linear circuits of which amplifiers are an example can add two signals together AND multiply both signals by a constant. In a multistage amplfier the gain of the stage is applied to the sum of the inputs in the case where there is more than one.

I must confess, given your original question, I'm at a loss to figure out what would convince you.