On 7/31/06, Mauricio Jancic wrote: > I wanted to keep the circuit as simple as it is now, but that's not a > mandate. What I certanly don't want to do is to make a circuit that has very > low efficiency, since it will have to run on batteries I've understand now. Maybe you could try the following trick: -use an LC filter between the transistor and the heater, and a high frequency range on the PWM -instead of PWM regulated voltage supply change the config for current supply (you need a pnp and a few resistors), then you'll not be forced to use a small range of the PWM resolution and the variation of the supply (which I understand it's a battery) in quite large limits will not influence the measurement accuracy as it probably does now. You probably know there are OP AMP with very small sourcing current, single power supply and rail to rail output, made just for battery applications... greetings, Vasile -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist