2.5 watt bipolar Triangular Wave Oscillator

[Farnarkler]

Hi guys. I am looking at building a triangular wave generator whose output will swing between +8.3 volts and - 8.3 volts driving 500Ma into an inductive 4 ohm load at around 1 hertz currently coupled through a 10 ohm 5 watt current limiting resistor. Vcc+ and Vcc minus will be +-12 volts. I think I can cobble together a oscillator using a dual TL082 jfet op amps but it would need an output stage and that is where I am a tad lost.

Any suggestions on how to approach this task would be greatly appreciated.

 

[Cabwood]

Try this. It might distort a little at higher frequencies, but 1Hz will be fine. Make sure you choose reasonably beefy transistors, because each will dissipate up to about 2W peak, 1W average, for a resistive load. If your load is very inductive this could be higher.

The op-amp is going to have to supply 10mA or so of current to the transistor bases, so it's going to get a little warm also! The TL082 might struggle a bit to supply that - if so, make the two transistors darlington types, to reduce the load on the opamp.

If you omit the feedback from the transistors' emitters, what you have is effectively a power op-amp, the output being the transistor emitters, and the inputs being the usual inverting and non-inverting inputs of the op-amp. It has a lot of cross-over distortion, but negative feedback will correct this. So, you'll probably be able to replace an op-amp in your waveform generator circuit with this circuit. The second circuit is a triangle wave generator with the integrating op-amp powered up in this way.

EDIT: Messed up circuit two - corrected and reposted

 

[Farnarkler]

Thank you so much. The second circuit looks ideal. Any recomendation on transistor selection? The load is inductive but I figured at this low frequency it should not be a problem.

 

[Cabwood]

Darlingtons:
NPN = TIP110
PNP = TIP115