OP AMP PWM

This is a really simple split power supply Op Amp PWM, only seven circuits. The large heat sink is necessary. The parts are easy to get too.

Step 1 Building the Circuit

As you can see it is small and simple. The pot should be at least 20k, and the more powerful transistor you use the better. A 1nF cap will produce 8 kHz oscillations a 150pF makes 75 kHz but the lower the capacitance the less reliable the circuit is. You can find your happy medium. =]    The yellow leads go to ground and the load. The LED's are for the diagnostic circuit.

Comments

[smewarik]

http://www.ewcoy.ru/

[JingleJoe]

Just a few things about this circuit, why have you got two 10k resistors in paralel giving feedback to the inverting input? surely one 4k7 resistor is the closest equivalent?
Additionally, doesn't the transistor need a base resistor? I know that using a lower power transistor without a resistor on the base, breaks it, is it not the same for high power transistors?

[pyrohaz]

If you put the motor between +v and the transistors collector, you would probably get less of a voltage drop :P put a reverse diode in parallel with the motor too to stop your tranny blowing :P Nice job :D

[jazzzzzz]

The diode and hooking the motor to V+ and the collector (the way I set up audio amps) are both great ideas. Thank you