nigelwright7557
- Joined May 10, 2008
- 532
Due to the input capacitance the yusually have resistors in series with the gate input on amplifiers.I'm thinking of playing with some MOSFETs to try to understand them better. I studied JFETs in college, and I think I have a pretty good handle on them. I'm only interested in digital modes at this point.
Power MOSFETs, on the other hand, are pretty strange in some ways. The gate capacitance issue, for example. What is a good approximation of where you start having to worry about the frequency of the PWM?
The other thing is the 10V on/off signal I keep seeing described for proper operation, with some lesser voltage mentioned for other devices. How do you determine from the data sheet what the control voltage is?
Looking at the IFR510, which is sold by Radio Shack, is a bit confusing. Is the V(GS) (which is +/- 20V) saying it needs 20V to switch fully?
BJ Micro has several, the IFR520 seems pretty similar (same V(DS)).
Assuming capacitance is an issue, I have to use drivers to drive the gates both positive and negitive quickly, such as a push/pull transistor pair?
I also notice all the power MOSFETS are N Depletion types. How common is this?
Thanks.
It can also be hard to bias push pull MOSFET amplifiers due to differences in gate turn on voltages and gate temperature/voltage drift.