[sdiy] input buffer question

[David G. Dixon]

> Curious why  your ASR input need any different treatment than any other
> modules?

Dave, to be brutally honest, I was looking at some schematics from a
"professional" module maker at a mate's the other day, and noticed that all
off-board inputs to opamps were protected.  I thought that perhaps I should
do the same.  Prior to that, I would have simply slapped the follower in
there without a care in the world.  Of course, most such inputs (at least,
in my modules) are attenuated, and this gives a path to ground.  However,
not so with the follower.  I'm sure it's overkill, but it makes me feel
better, so what the hell?

> BTW, the opamp may already have protection diodes to the rails.  With
> the series resistor on the input to limit current through the internal
> diodes, are external diodes really necessary?  I don't know, just asking.

According to the schematic in the datasheet, TL07x does not have protection
diodes on the inputs.  It has output short circuit protection (and, hence,
the 1k output resistor we typically put in there is not strictly necessary,
but I still do it anyway), but the inputs are just bare JFET gates.