Don's source follower

[Don Tillman]

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