[help] unity gain buffer?? to stick on the end of circuits?

[ulysses]

A unity gain buffer, which has a high input and low output Z, will sometimes be used as a line driver to preserve the full frequency response of the signal.

is the very last sentance on jacks page on impedance: http://www.muzique.com/lab/imp.htm

does anyone have a schem of a unity gain buffer with high input and low output Z?

im not looking for a complete circuit, just a snippet i can add onto the end of other people circuits with bad output impedance.. preferably with a simple opamp like a tl071/2

EDIT: just to clarify, i know how to get unity gain buffer out of an opamp, its the high input / low output Z bit that i am unsure about..

cheers
ulysses

[GibsonGM]

Any opamp set up with gain=1 will be a hi-Z input, low-Z output.  By definition, a buffer doesn't amplify the signal, altho occasionally they will be used in a recovery type application, so 'unity gain' is kind of redundant.

There are a ton of transistor buffer circuits, too - 3 resistors and 2 caps....check out AMZ, and Tim Escobedo's site (in the links section).  GGG had a transistor buffer up at one time, too.   Maybe you missed this:
http://www.muzique.com/lab/buffers.htm
Has 'em all! 
Enjoy,

~Mike

[ulysses]

thanks mike i will check them out - had not read them

cheers
ulysses

[soulsonic]

My favorite for driving outputs is the opamp type.

[JHS]

No buffer has unity gain, 0.7 - 0.8 x gain is what you get from a buffercircuit, for unity gain a small recovery stage after the buffer is needed and nearly all buffercircuits alter the sound.

JHS

[Gus]

define bad output Z.  Or what do you want to "fix"

[alanlan]

No buffer has unity gain, 0.7 - 0.8 x gain is what you get from a buffercircuit, for unity gain a small recovery stage after the buffer is needed and nearly all buffercircuits alter the sound.

JHS

I beg to differ dear boy!
Op-amp follower = unity gain
Emitter follower = just short of unity gain but as near as dammit for most purposes
As for sound alteration, well it's a bit arguable I suppose but a good quality op-amp will produce practically inaudible distortion and frequency response alteration.  What sometimes does get confused is that inserting such a circuit into an otherwise unbuffered set-up probably will alter the resulting sound - after all, if it didn't you wouldn't need one by definition!

[GibsonGM]

Right...some tweaking of caps or what have you may be required to reclaim whatever sound you were looking for - things could be brighter, punchier.  Most of us like that, though, he he....