# Why it is called DC-Gain, while doing AC analysis

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#### lsdee

##### Newbie level 3
Why it is called DC-Gain, while doing AC analysis in Cadence？

I was confused.

What is the definition of DC gain?

And why we could get it from the AC analysis in Cadence？

#### dick_freebird

Why it is called DC-Gain, while doing AC analysis&#65311

I'd guess just sloppy expression. Though your small signal
gain, extrapolated back to 0 Hz, should match a true DC gain.

Maybe "Gain at a sufficiently low frequency that it is the same
as DC" doesn't roll so trippingly off the tongue.

#### lsdee

##### Newbie level 3
And is there any connection between that "DC" and "AC"?

#### jesseyu1984918

##### Newbie level 6
DC means no capacitance and inductance while AC have

#### master.ckt.breaker

##### Newbie level 6
DC Gain implies Gain at 0 frequency.
We know that,
Gain Bandwidth Product = DC Gain * 3dB BW = 0dB gain * UGB (Unity Gain BW)

May be from this expression, the term DC gain might have arrived. Just a guess...:|

#### vistapoint

##### Member level 5
AC analysis is not run point by point in time domain. It's frequency sweep based on transfer function or in freqency domain. DC gain when f=0.

You don't have to get it from AD analysis. You may get from other analysis but you'll find it takes longer time especially when you want to compare different frequecies.

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lsdee said:
Why it is called DC-Gain, while doing AC analysis in Cadence？

I was confused.

What is the definition of DC gain?

And why we could get it from the AC analysis in Cadence？

#### edafisher

##### Junior Member level 3
you may also call it "low frequency gain" as Gray and Meyer.

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