Power project

My project's goal is to design a circuit that outputs a high frequency high power signal into a transducer load. Specifics:

* up to 100Vpp square wave (sine wave is ok instead if it's easier, variable voltage nice to have but fixed ok for now)
* output power up to 100W peak, 40W continuous
* frequency up to 500kHz (tunable is nice to have but fixed ok for now)

I have considered a few possible approaches so far, including:

* half bridge driver IC plus power MOSFETs
* Class D amplifier with output filter removed

Eventually I want to design a PCB (done one before for HB-LED) but for now breadboarding or using reference designs / eval boards is preferred. I've been looking a fair amount at the IRF and National websites.

I am looking for suggestions on how to proceed.

http://www.cirrus.com/en/products/apex/index.html

I would recommend contacting the guys at Cirruslogic group that used to be Apex microtechnology see the link above. Use one of their evaluation boards and then feed it with what ever you like a 555 timer or a Variable sine wave generator circuit or... then use a variable gain so you can set the circuit gain, thus the output voltage and you can adjust the drive frequency to get the variable frequency you need. I think you can build all or most of it on the APEX eval board. You might want to tell them what the load is like in terms of reactive components making up the load so you can add the right protection. They have apps engineers which can help you design the entire thing if you need them to. if this is a one off for test equipment or something that's not mass produced then you can use a function generator to feed the power op amp stage. I would not recommend class D as I don't know what your load would do with the high frequency components in the output - conventional class AB is likely going to be better unless you need the efficiency.

You have given us a reasonable idea of what your power supply needs to produce, but nothing about what the power input parameters are. A power supply is a converter circuit. You therefore need to know what it needs to convert from just as much as what it needs to convert to.

I can use a benchtop variable power supply for the time being. Eventually I will want to go to rechargeable battery powered operation. I would like to first prove the concept that a compact replacement of an RF power amplifier is possible.

In that case, a transformer output stage comes to mind. Your input voltage is apparently low, so you can use a center tapped primary to make things easy. The center tap goes to the input power supply with a low side switch on each end. Pulse each end 180 degrees out of phase with some dead time.

At 500 kHz you should be able to set up resonance at a reasonable size. That would help with efficiency and reduce harmonics on the output.