Sine wave generators

Why would you want an IC? YOu can't get much simpler than ann audio sinewave oscillator, and the bulk of the components will be passive, to determine the frequency.

You'll find that most of the audio generator ICs will generate a sinewave through indirect means, ie they start with a triangle and then distort the waveform till it's a reasonable sinewave. That sort of thing is great when you want multiple waveforms out of the oscillator, and when you want a wide-range oscillator since a good sinewave oscillator will tend to be cumbersome to vary in frequency since multiple components will need varying. But what's good for one thing isn't good for others, and the sinewaves that come out of such arrangements tend to be less than perfect. If you need a single frequency sinewave, or at the most a few frequencies, likely you want the sinewave for some specific use, and you want that sinewave to be fairly pure.

A single transistor and a phase shift network will make a nice sinewave oscillator if you only need a single frequency. If you need more than one, but still just fixed frequencies, use a few transistors and make separate oscillators; it's easier to switch power to each device than switch the frequency determining elements.

Wien bridge oscillators are the cat's meow for sinewave oscillators, and they were made with single tubes in the old days. An op-amp tends to be the active device these days, and again, for a few fixed frequencies it may be easiest to just build a few oscillators.

Michael

"Roger Dewhurst"

** Kiwi Groper Alert

** The easiest way is to make a square wave oscillator first ( 555 or op-amp) and follow that with a sharp, low pass filter to remove the harmonics at 3, 5, 7, 9 ... times the fundamental.

Eg:

A trim pot will permit small ( +/- 10% ) frequency adjustments.

Add an extra RC filter at the output for lower THD.

...... Phil

You can use a dual opamp for reasonable low frequency sinewave oscillators.

See my example at:

-Bill

I am looking for a sine-wave tone generator that can emit pure sine- waves at ultrasonic frequencies up to the maximum frequency that can travel through air on earth atmosphere + 1 KHz. So 1 KHz abve the max that can exist in earth's air.

What are you using for a transducer?

** Change your GG settings - Bob.

Your post appears with no clue as to whom you are addressing or about what.

....... Phil

You don't mention the intended application or the quality needed. The Intersil ICL8038 function generator is a one-chip solution (plus a few passive parts) that gives sine, triangle, and square and is easily tuned over the audio range. Distortion is about 1%, typical of all "function generator" oscillators, which shape the sine from a triangle.

Most low-distortion circuits have the drawback that they require tracking potentiometers for tuning, though these days digital pots with "perfect" tracking make that much easier.

The simplest way to make low-distortion signals iswith your Windows computer and sound card. You can use the signal generator in my Daqarta software to make sine waves with much lower distortion than most any bench-top oscillator you are likely to afford. Plus you can make all sorts of other waveforms, and you can apply AM, FM, phase modulation or PWM, bursts, sweeps, etc... all at once, if you need to! You can have 4 of these oscillator "streams" per left/right channel, and one stream can modulate others to get dizzying complexity.

Daqarta is nominally shareware, but the signal generator is essentially freeware since it continues to work after the trial expires. You are welcome to use it this way as long as you like.

Please let me know if there are any questions or problems.

Best regards,

Bob Masta D A Q A R T A Data AcQuisition And Real-Time Analysis

Scope, Spectrum, Spectrogram, Signal Generator Science with your sound card!

fixed

off-the-shelf

Thank you. I am thinking of a burglar deterrent which would require two large speakers, say 300 watt, producing two tones separated by 7 to 10 Hz. The two tones could be low, middle or high audio frequency. I suspect that two low frequencies would be easiest. Other posters have given me some ideas on generating the sine waves but clearly these need to drive some large transistors to get the wattage into the speakers. Have you any ideas on this?

Roger

if I happened to be your neighbor and hat system would cut loose in the middle of the night, I would sue you for your last penny (or dollar cent/euro cent). :)

Here you could not sue. You could complain the council noise control people the next day. They would come round in a day or two to listen to the noise and perhaps test it with a decibel meter! It is more likely that the burglars would go to the police to complain that they were assaulted!

R

I fear you may be on the wrong track with your basic concept. You state that you want a frequency *difference* of 7-10 Hz. That won't cause any particular discomfort, just an audible beat frequency. Note that beats are an auditory phenomenon, not a physical one: The beat frequency (barring speaker nonlinearities, etc) only exists inside your head. (Yeah, you can "see" the beat rate in the waveform of a scope, but it's not there in the spectrum. Check it out with Daqarta, if you are curious about this.)

On the other hand, if you create real sound in the 7-10 Hz range, you may be able to excite resonances in the human viscera that are alleged to cause extreme discomfort. The catch is that it is quite difficult to move enough air to get loud sound at frequencies this low. This is well below the resonant frequency of most woofers of any reasonable size.

The early experiments that turn up these visceral resonances were with large steam whistles. Later, NASA used large electromechanical drivers to shake a person sitting in a chair. (Like sitting on a giant woofer!) The were attempting to determine human limits for early space flights.

Best regards,

Bob Masta D A Q A R T A Data AcQuisition And Real-Time Analysis

Scope, Spectrum, Spectrogram, Signal Generator Science with your sound card!