PWM with 555 am I ingenious or barmy ?

[Dr.EM]

Here is a quick hand drawn diagram of the voltage controlled PWM system I used earlier to control the heating wire at 3A. It was run off of a 14v cordless drill battery, but should work from around 8-34v. I used a TL084 quad op-amp and most resistors were 1% (this is only really important for the half supply 10ks and the triangle wave amplifier to avoid clipping and give the highest level). The MOSFET switches fast enough even with the 15k gate resistor, as the frequency of the circuit is only 150Hz (this is ideal for most PWM applications, and i've tried this with bulbs, heating wire, motors and computer fans). I intend to post this under projects soon as I think quite a few will find it useful.

EDIT: missed a protection diode off of this, it should be included. Also, most motors generate a lot of noise and will need some snubbering to be used sucessfully. 100nF bypass caps on the op-amp are wise too.