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Electronics => Projects, Designs, and Technical Stuff => Topic started by: 741 on April 29, 2018, 07:42:22 pm

Title: How are small-signal linear MOSFET amplifiers designed?
Post by: 741 on April 29, 2018, 07:42:22 pm

How are small-signal linear MOSFET amplifiers designed?

Eg, Source follower, common source. We no longer have the Vbe approxiamtion, and device parameters vary quite widely.

For a bipolar, we can assume (say) a gain of at least 100, and Vbe ~= 0.65, and get some way using basically just that. I'm ignoring Early effect, tempcos - but at least you can have a stab at it.

Now, say I have a say a TSM2302, (Farnell 2628137), how do I design
(1) A source follower
(2) A gain of 10 amplifier using that?

I'm guessing I have to start by assuming a minimun transconductance, but how about biasing etc?

Title: Re: How are small-signal linear MOSFET amplifiers designed?
Post by: EmmanuelFaure on April 29, 2018, 08:19:48 pm

http://www.mhhe.com/engcs/electrical/neamen01/ch06.pdf (http://www.mhhe.com/engcs/electrical/neamen01/ch06.pdf)

Title: Re: How are small-signal linear MOSFET amplifiers designed?
Post by: Wimberleytech on April 30, 2018, 03:17:57 am

I am scratching my head as to "why?"

A source follower would be straightforward.  The input could be easily biased to guarantee operation over the variation of VT and transconductance.

Title: Re: How are small-signal linear MOSFET amplifiers designed?
Post by: 741 on May 01, 2018, 09:00:25 am

Thank you Emmanuel, that looks ideal.