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#### yonzzan

##### Junior Member level 3

I was wondering why AC magnitude is 1 V when simulating circuits in cadence.

why not 2, 3 or 4??

#### safwatonline

Av=Vout/Vin
if Vin=1
Av=Vout

anhnha and yzzrlzc

Points: 2

### anhnha

Points: 2

#### taik

##### Member level 3
it can be... just that 1 makes it simpler...

as seen from the formula that safwatonline entered...

#### yonzzan

##### Junior Member level 3
That's what I understood too. however, when I increased the magnitude, then gain became bigger. that doesn' t make sense, isn't it supposed to be reduced because vin is inversely proportional to gain????

#### safwatonline

AC Gain is constant whatever value of ac input.
so for a constant gain, Vout=Constant*Vin.
so increasing Vin will increase Vout but doesn't affect the gain

yzzrlzc

### yzzrlzc

Points: 2

#### enchanter

##### Member level 2
The simulation result of Spectre mag(V) means gain when input AC Magnitude is 1V? Because I was wondering why my 1.8V NAND can get more than 20 V output.

#### checkmate

When you do an AC analysis, the circuit is linearized at the operating point.
The meaning of linearized is that it no longer consider non-linear effects, such as limits placed upon component breakdown, or supply limits. Another implication is that the linearized equations apply to both large and small signal alike.
In simple words, for an amplifier with gain 1000, the ac analysis will show that an input of 1mV gives 1V, and an input of 1MV gives 1GV!

Points: 2

Points: 2