# Sine wave generators

Discussion in 'Electronic Basics' started by Roger Dewhurst, Mar 31, 2007.

1. ### Roger DewhurstGuest

What is now the easiest way to go for sine wave oscillators to work on fixed
frequencies near the middle of the audio spectrum? Are there off-the-shelf
chips that will do the jobs?

R

2. ### Michael BlackGuest

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

3. ### Phil AllisonGuest

"Roger Dewhurst" <>

** 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:

http://www.national.com/nationaledge/jun04/article.html

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

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

....... Phil

4. ### Bill BowdenGuest

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

See my example at:

http://ourworld.compuserve.com/homepages/Bill_Bowden/page8.htm#phase.gif

-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.

6. ### BobGGuest

What are you using for a transducer?

7. ### Phil AllisonGuest

** Change your GG settings - Bob.

........ Phil

8. ### Bob MastaGuest

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
www.daqarta.com
Scope, Spectrum, Spectrogram, Signal Generator

9. ### Roger DewhurstGuest

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

10. ### Sjouke BurryGuest

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).

11. ### Roger DewhurstGuest

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

12. ### Bob MastaGuest

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
(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

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
www.daqarta.com
Scope, Spectrum, Spectrogram, Signal Generator