3
\$\begingroup\$

For a test of a filter and video transmitter gear, I need a variable frequency (potentiometer adjusted) sine or square wave oscillator, adjustable from about 1 to 10 MHz. Output about 1Vp-p okay, but I could reduce a higher output. I don't have many parts at the moment; so I need the cheapest way to do this. I have a lot of NOR gates lying around and I'm thinking of a ring oscillator but when I try to make them adjustable they become unstable.

\$\endgroup\$
0

1 Answer 1

4
\$\begingroup\$

How about an oscillator around a Schmitt-Trigger inverter? Capacitor on input, resistor from output to capacitor, done.

relaxation oscillator

\$\endgroup\$
6
  • 1
    \$\begingroup\$ has to be a schmitt-trigger; without the hysteresis it will just settle at a voltage somewhere near the middle of the rails. \$\endgroup\$
    – JustJeff
    Apr 29, 2011 at 1:33
  • \$\begingroup\$ Is there any drawback to using an op-amp based schmitt trigger over one of the 74HC14s? \$\endgroup\$
    – drxzcl
    Apr 29, 2011 at 7:53
  • 1
    \$\begingroup\$ @Ranieri - not really. I posted this because it's the absolutely minimum component count solution. It has fixed trigger levels, however, in the opamp version you can set the trigger levels yourself. \$\endgroup\$
    – stevenvh
    Apr 29, 2011 at 8:01
  • 1
    \$\begingroup\$ Getting an op amp circuit to oscillate at 1 MHz to 10 MHz will be very difficult! \$\endgroup\$ Apr 29, 2011 at 10:07
  • 1
    \$\begingroup\$ @Leon - you're right (I forgot the frequency requirements for a moment.) \$\endgroup\$
    – stevenvh
    Apr 29, 2011 at 13:14

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.