Don's source follower

[tomg]

Nifty Don, Looks a little like the fet followers Buchla used in
his LDR BP filter. Thanks for sharing.

Tom



> Hey, electronics folks...
> 
> This is a rough sketch of a building block I'm starting to use a lot
> lately; it's a complementary source follower:
> 
> http://www.till.com/random/follower.gif
> 
> The FETs are hand-matched.  One circuit I have here matches them to 
> Id = 1.8 mA at Vgs = -0.4 V.  For more drive you can match to a higher
> current and reduce the values of the source resistors, even to zero.
> 
> While it doesn't come close to the performance of an opamp voltage
> follower for control voltage applications, for a high fidelity audio
> path this follower has about ten really interesting features.  (Name
> them!)  Typical applications would be a buffer for guitar pickups, an
> input buffer for audio processors, an OTA output buffer, a follower
> stage for a Sallen-Key active filter, that sort of thing.
> 
> Question: Has anybody seen this circuit used before?  I've never seen
> anything like it, but it's so simple I can't believe I invented it.
> 
>   -- Don
> 
> -- 
> Don Tillman
> Palo Alto, California, USA
> don at till.com
> http://www.till.com
>