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Unread 23-12-2005, 10:49
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Re: Circuit design help - power supply - Non FIRST

I'm well aware of the potential dangers, and never work with hydrogen indoors or around any sources of heat. I also ground myself before I work on the generator to prevent static discharge.

That said, I've been doing a lot of research on this topic over the past few days.

I know there are function generator kits out there (kit 6023 KT at MPJA, for example or the 3023 at Quasar) which use a "4 core" LM348 op amp to generate sine, square, and triangle waveforms. These use an op amp with an identical pin-out to the MXL1179 from Maxim IC, which can handle very high current and voltage - now, at first I thought that I could simply replace the IC, but then I thought about it and there's a) no way the traces would hold up to 30 amps, b) I'd still need high wattage resistors, and c) I don't know how to set up offset voltages.
That led me to think about the way PWM works, at least from my primitive knowledge of it. If there were some way for me to set a bias voltage on that function generator kit, I could change the potentiometer for the range I want and use a MOSFET to control voltage, couldn't I?

So what I'm thinking I'd like to do is this:
Function Generator (powered by 9V or similar) - pseudo sine wave out to a rectifier - to a MOSFET.

Am I thinking along the right lines? Is there any way to use the kit I linked with an offset voltage easily? Also, I'm not sure of the peak-to-peak voltage on the kit, and I assume my MOSFET selection should be based upon that and the offset (ie., 6V/30A MOSFET if it's 3V peak to peak and a 3V offset voltage).

The only problem I forsee with this circuit is the voltage in the secondary circuit (through the MOSFET) being susceptible to changes in the voltage of the control circuit. It also seems pretty inefficient.