[sdiy] simple transistor buffers?

[Harry Bissell]

emitter follower always has about a .7V drop at the emitter
(the b-e drop).  Its good for increasing current but does not
preserve voltage levels.

Some J-fet followers do a bit better than this...

The op-amp follower is the standard if you need precise voltages.



----- Original Message -----
From: dan snazelle <subjectivity at hotmail.com>
To: synth-diy DIY <synth-diy at dropmix.xs4all.nl>
Sent: Fri, 19 Nov 2010 11:02:04 -0500 (EST)
Subject: [sdiy] simple transistor buffers?

So i am working on a circuit where there are a bunch of outputs. to save space/opamps I decided it would be nice to use transistor buffers (emitter followers)

however when i switched to what i THOUGHT was a usable buffer, the output gain (versus opamp followers) dropped drastically.

let me see if i understand this properly. ( i dont think i do)

if i want to buffer an lfo that is running between + and - 12 volts, I was putting the oscillator wave through a 1k resistor into BASE. I was then putting the collector to +v. What confuses me is what to do with the emitter other than
this is where i take the output and a resistor to ground or -v should connect here.

I am not sure if i should put emitter to GROUND or to -v through say a 10k resistor.


Also, do I need to put a cap before the input to the base?


any help and or links to schematics for reference highly appreciated




thanks!



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-- 
Harry Bissell & Nora Abdullah 4eva