Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!mips!ptimtc!nntp-server.caltech.edu!lakata
From: lakata@nntp-server.caltech.edu (Mark T. Lakata)
Newsgroups: sci.electronics
Subject: Help with op-amp follower
Message-ID: <1991Jun23.230350.27027@nntp-server.caltech.edu>
Date: 23 Jun 91 23:03:50 GMT
Organization: California Institute of Technology, Pasadena
Lines: 22

What would cause high-frequency (MHz) oscillations in an op-amp
follower (output connected to inverting input)?  My circuit worked
fine for a while, then developed this oscillation that would sometimes
go away when I touched the contacts on the back side of the circuit board.
I'm using an LF356 op-amp on a wire wrap board.  The oscillations happens
both with no input attached and with an input attached.

               sine wave input
	       5vpp, 10 - 10^6 Hz input
                 |
               =====  special capacitor 
                 |
                 |       |\
                 +-------|+ \
		 |       |    \______ out
        .01 uF =====     |    /  |
		 |    |--|  /    |
		 |    |  |/      |
	        gnd   |__________|

Opamp supplied with +/- 7 volt supply.
Thanks, Mark