The thing to remember is that the gate on a mosfet (or any fet, I suppose) is a CAPACITOR. You have to charge it to a sufficient voltage to bias the mosfet; the charge time depends on the resistance or current limits of the driving circuit. You also have to bleed off the charge to shut it off again.
Also, mosfets as switches are either on or off, both of which generate minimal heat (low current or low resistance). However, in the in-between state, the mosfet will generate a lot of heat. You want to minimize this by minimizing the time spent in that state. Power mosfets (and hexfets) use many individual fets in a parallel array to handle the high current. However, this also increases the gate capacitance, which lowers the effective frequency response for a given drive circuit. For an amp, you probably want to look at the Vgs versus Rds curve, pick the spot you're going to run the amp at, and see how much actual current (and thus heat) you'll be seeing. _______________________________________________ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
