[sdiy] Inverting Amplifier as a Buffer Output.

Harry Bissell harrybissell at wowway.com
Thu Jun 24 16:32:08 CEST 2010


If you have a modular synth (I assume this is the case...) you might have
multiple outputs, each with an 'outty' resistor. If all your input resistances
are the same (as I said earlier, 100K)... then when you calibrate that voltage
source you will remove the gain error.

even 10 ohms in series will cure cable capacitance instability... thay would be 
.01% error...

maybe you have a really really really good VCO ???   :^)

A or B will work. I need to consider the layout like you mentioned... maybe "b"
does lay out better...

H^) harry


----- Original Message -----
From: David G. Dixon <dixon at interchange.ubc.ca>
To: 'David G. Dixon' <dixon at interchange.ubc.ca>, 'Oscar Salas' <osaiber at yahoo.es>, synth-diy at dropmix.xs4all.nl
Sent: Thu, 24 Jun 2010 00:11:50 -0400 (EDT)
Subject: Re: [sdiy] Inverting Amplifier as a Buffer Output.

> I used to use A all the time, but now I use mostly B, because I found that
> it is a helluva lot easier to lay out on the PCB, with or without the 10pF
> cap (which I always make provision for, whether I use it or not).  I have
> noticed no difference in how my circuits perform.
> 
> My $0.02 (probably only worth $0.01).

Oh, and I almost forgot to mention, if you are using it to buffer a
precision CV signal (like something which will be fed to the 1V/oct input of
a VCO, for example) then definitely use B.  The "outty" resistor in A will
cause tuning errors by creating a divider with the input resistor at the
receiving end.  The "inny" resistor in B will not.

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-- 
Harry Bissell & Nora Abdullah 4eva



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