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Design >> Analog Design >> 3-stage amplifier vs two-stage amplifier
https://designers-guide.org/forum/YaBB.pl?num=1423131345

Message started by ywguo on Feb 5^th, 2015, 2:15am

Title: 3-stage amplifier vs two-stage amplifier
Post by ywguo on Feb 5^th, 2015, 2:15am

Hi Guys,

What's the advantages of 3-stage amplifier considering bandwidth and slew rate compared with 2-stage amplifier? This question looks like a very open discussion. Any comments are appreciated.

Yawei

Title: Re: 3-stage amplifier vs two-stage amplifier
Post by raja.cedt on Feb 5^th, 2015, 4:23am

It's hard to answer.
You will always end up with lower bandwidth in 3 stage amp, because 3 non dominate poles compared to 2 stages. Slew rate mostly architecture dependent.

Thanks,
Raj.

Title: Re: 3-stage amplifier vs two-stage amplifier
Post by Rakesh on Feb 5^th, 2015, 7:53am

Hi,
If you want to compare with the same DC gain as the 2 stage amplifier, then you might be able to increase the bandwidth by appropriately distributing the gain across the stages. However it still depends on the architecture and the load. Slew rate depends on the architecture.

Rakesh

Title: Re: 3-stage amplifier vs two-stage amplifier
Post by loose-electron on Feb 6^th, 2015, 11:00am

Depends on performance criteria and process considerations.

Define performance end to end and then fit a solution into it is my perspective.

Title: Re: 3-stage amplifier vs two-stage amplifier
Post by carlgrace on Feb 6^th, 2015, 3:26pm

Not sure if there are any advantages regarding BW. A single-stage amplifier is always fastest in a given technology, then 2-stage, etc because of the reason Yawei said.

I've only seen people use 3-stage amplifiers when they needed super-high DC gain.