<HTML><BODY style="word-wrap: break-word; -khtml-nbsp-mode: space; -khtml-line-break: after-white-space; "><BR><DIV><DIV>On May 1, 2006, at 9:49 AM, Aaron Lanterman wrote:</DIV><BR class="Apple-interchange-newline"><BLOCKQUOTE type="cite"><P style="margin: 0.0px 0.0px 0.0px 0.0px"><FONT face="Helvetica" size="3" style="font: 12.0px Helvetica">Speaking of which, I've got another student working on a voltage-controlled crybaby circuit. I turned him onto using a gyrator to replace the inductor. He grabbed an off-the-shelf crappy op amp (LM301, maybe? I don't recall the number), and it gave him 5 times the mH he was wanted to get. Then I gave him a TL08something, he swapped that in, and it gave him what he wanted.</FONT></P> </BLOCKQUOTE></DIV><BR><DIV>Maybe you already knew this, but just in case you didn't: </DIV><DIV><BR class="khtml-block-placeholder"></DIV><DIV>The LM301 is a non-frequency-compensated opamp, and in most applications, must have its high frequency response compensated with an external capacitor. Without the cap, the amp with have a very different frequency response than any of the typical internally-compensated opamps that we are used to (pretty much all modern opamps, with just a few exceptions). It could also have serious oscillation problems, depending on the gain factor and type of circuit configuration. This means an LM301 will likely not work as you might expect a 741 or TL081 to work. This could explain why the gyrator circuit responded so peculiarly..</DIV><DIV><BR class="khtml-block-placeholder"></DIV><DIV>To make the LM301 behave like a standard amp, usually it just means connecting a 30pF cap between pin 8 and pin 1.</DIV><DIV><BR class="khtml-block-placeholder"></DIV><DIV>See the LM301 data sheet for tips on external compensation:</DIV><DIV><BR class="khtml-block-placeholder"></DIV><DIV><A href="http://www.utdallas.edu/~hellums/docs/JournalPapers/LM101A.pdf">http://www.utdallas.edu/~hellums/docs/JournalPapers/LM101A.pdf</A></DIV><DIV><BR class="khtml-block-placeholder"></DIV><DIV><BR class="khtml-block-placeholder"></DIV><DIV>BTW, ARP synths are FULL of LM301's.</DIV><DIV><BR class="khtml-block-placeholder"></DIV><DIV><BR class="khtml-block-placeholder"></DIV><DIV>MB</DIV><DIV><BR class="khtml-block-placeholder"></DIV></BODY></HTML>