Stuff you wanted to know but were afraid to ask

[JTEX]

How in the hell do you calculate the gain on this output section on the Informant/DRV? Normally on a noninverting gain stage like this you'd take R14 and divide it by R13 then add one. Not only is R13 way bigger than R14, it's going to ground with no capacitor instead of vref.
View attachment 83430

This is basically a unity gain buffer. R13, C10 and R14 could all be eliminated and replaced with a simple short between pins 6 and 7 and the circuit would work almost exactly the same. I have no idea why they're there. Maybe as placeholders in case you want to mod it?

 

[cdwillis]

That's what I thought at first, but then I thought maybe I'm just not clever enough to understand it. I was making a Rat style pcb recently and used a TL071 for the buffer instead of the jfet then I added the option of making it a gain stage for more output volume.

I built an Informant then I ended up trading it. I can't remember how the volume compared to my Rat.