Function / Waveform Generator Design using op-amps

[Honeybee]

HI

Does anyone have any idea how to design a function generator using op amps to produce triangular, sine, square and ramp waveforms?
I also need to design for a level shifting of ± 1V.

The sine is produced by an oscillator and the square by an astable multivibrator.
I'm having problems with the ramp and traingular waveforms in particluar. i have no cct for the ramp and when I try to integrate the square waveform, I get a triangular waveform but it acts like a ladder.

Any hints will be greatly appreciated.

Honeybee

 

[flatulent]

Re: Function Generator Design

Are you really restricted to op amps? The triangular and saw tooth can be done with discrete transistor current sources driving a cpacitor. The saw tooth sharp edge by a transistor discharging the capacitor. Then use the op amps for inversion, gain, and DC offsets.

 

[Honeybee]

That sounds like a pretty good idea, but could you please eloborate in terms of the actual circuit connections.

Honeybee

 

[flatulent]

The current sources are just like those used in op amp design. One way is to use a mirror circuit to drive the capacitor and make the variable current source driving the mirror. This will change the slope of the voltage on the capacitor. You can use a comparator to detect when the capacitor reaches the limit and switch to the other polarity of current drive or the discharge transistor. Change the frequency with the control of the current magnitude.

I am assuming that you have manual controls turned by a human operator to get the desired results.

If you want to be very expensive you can use DDS type methods which are very precise and used in commercial instruments costing several thousand euros or dollars.

 

[nicleo]

If you're not restricted to op-amps, probably you would like to study these ICs ( **broken link removed** , **broken link removed** ) whether they suit your application.

 

[Honeybee]

The use of ICs is not allowed, sorry I forgot to mention it before.

 

[IanP]

In the atached GIF file you will find 3 basic circuits of op-amp based generators.