Question about AC magnitude in Cadence..

[yonzzan]

cadence ac magnitude

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

why not 2, 3 or 4??

Thanks for answering my question ahead

 

[safwatonline]

ac magnitude in cadence

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

 

[taik]

it can be... just that 1 makes it simpler...

as seen from the formula that safwatonline entered...

 

[yonzzan]

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

 

[enchanter]

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!