[Pars]

I'm currently building a test board of cetoole's I/V stage, and had tacked on this PSU/regulation section from rbroer's less simple I/V stage for a TDA1541a. I thought I had things to a manageable point with the I/V stage until I made the fatal error of putting my scope on it

Here is the schematic of this section:

And the entire board layout:

I have an oscillation of ~100MHz (0.5 div @ 0.02uS per div) on the output. It even shown up on the ground (is this what they refer to as "ground bounce")? After going over the I/V board and removing transistors from sockets, checking lead lengths, cleaning etc., I still could not get rid of it. I pulled Q1 and Q2, and jumpered the emitter to collector pads to run it straight off my bench PSU. No oscillation, so I guess it is the PSU portion that is causing it.

I did some reading online, and they talk about a base stopper resistor, which I assume are the 100 ohm R3 and R4 shown. It was mentioned that these may need to go up into the K range, so I removed the 100 ohm resistors and replaced with 1.33K. Still no change. Any suggestions?

Thanks,

Chris

 

[Pars]

Nevermind, I found the problem. I had omitted a pair of 470uf caps right at the I/V stage input... tack soldering these in cured the problem. DOH