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Design >> Analog Design >> ac simulation of gain boost amplifiers
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Message started by Dennis Min on Feb 6^th, 2006, 12:31am

Title: ac simulation of gain boost amplifiers
Post by Dennis Min on Feb 6^th, 2006, 12:31am

hi, all

Attatched please find a high gain amplifier schematic with the gain boost scheme.
I wonder to know how to perform ac simulation of the pmos and nmos gain boost amplifiers, such as the gain vs frequency and phase margin.
Is the boost amplifier a transresistor opamp?
Tks.

Title: Re: ac simulation of gain boost amplifiers
Post by zhonghan on Feb 6^th, 2006, 6:32am

a folded voltage omamp ?

Title: Re: ac simulation of gain boost amplifiers
Post by vivkr on Feb 7^th, 2006, 3:34am

Hi,

The simulation can be done the same way as for any other opamp. The simplest scheme however is to
leave the gain boost amps the way they are, and measure its AC performance in closed-loop.

Remember that the gain and phase of the amplifier (for the same load) remain the same whether it is tested
in closed loop or open loop. So, you can define gain as

VAC("out")/(VAC("inp")-VAC("/inm"))

The gain and phase of this quantity give you all the information you need.

As to the realization of the boost amp, it can be made using any conventional topology (common-source, differential pair,
folded-cascode etc.) depending on what kind of gain you want and other constraints.

Hope this helps.

Regards
Vivek