Simple oscillator circuit

You haven't mentioned what your ultimate goal is, but I'm guessing that this is to be part of something that is experimental... maybe in need of some adjustments (the ~10% variance you mention) before you get things to work just right.

If so, you might want to use a function generator during the development phase. Then when you are sure you can get the desired result, you can replace that with a circuit.

If you don't already have a function generator, you can use the free Daqarta Generator, which works with your Windows sound card. To get to 30 kHz, you'll need a sound card (or built-in chipset) capable of sampling at 96 kHz. Most systems will do that these days, but older systems may be limited to 48 kHz, or even 44.1 kHz if it is *really* old.

Sound output frequency on any digital system can't exceed half the sample rate, but at 96 kHz you should have no problems getting to well past 30 kHz. Note, however, that there are some systems that can sample at 96 kHz, but which apparently have analog filters that limit the output frequency to ~20 kHz. You can easily test if yours is one of these via a "loopback" cable from output to input.

Although this may all sound rather cumbersome compared to a neat little circuit on a breadboard, the advantage is that you can easily change things experimentally. Besides fixed-frequency sines, you can change waveforms at the click of a button, or add various types of modulation (AM. FM, Phase) or tone bursts or sweeps. You can even create a band of noise that covers a chosen frequency range.

Then, once you find the ideal signal for your project, you can cast it into hardware. Otherwise, if you start with the hardware and the initial design doesn't give the desired results, you can waste a lot of time pursuing dead ends. For example, if you think *maybe* it would work better with an FM warble, that's not easy to add to your existing design. But if you knew from the function generator tests that it was needed, you could get the right circuit for the job.

Note that the Daqarta Generator really is absolutely free. After the trial period, the

Best regards,

Bob Masta DAQARTA v5.10 Data AcQuisition And Real-Time Analysis

is an op-amp

Yeah, You'd certainly have enough current to turn the light bulb on! (to OP if you don't try Phil's idea you do need an opamp with a decent amount of current drive. (at least that's my experience...) you might check out AN43 from Linear. J. Williams does a nice job describing the operation... page 29 and beyond.)

Say has anyone used the LM1875? Is it any better/worse than the LM675? (I've always found little bits of cross-over 'crap' on the LM675)

George H.