mdrejhon:
This looks like the right circuit to drive a 12V 3A load for my project (LED ribbon). Can I drive the load at 2Khz (switch on/off 2000 times a second) with this circuit, without wrecking the FET?Also, are there alternatives to this circuit, e.g. a single component that integrates an equivalent of this whole circuit into it -- logic-controlled high-amperage 12V amplifiers in a single package? (even if a few dollars extra)
The only issue with my circuit is that 1k pull-up resistor - it limits how fast the IRF3205 can turn on. The total gate charge is about 150nC for the 3205 so it'll take on the order of 10us to pull high - at 2kHz that means about 2% of the time will be in this slow switching zone. For 12V and 3A that'll be OK (the rough estimate for dissipation during switching is VI/4 - so at 2% of the time that averages 0.18W)
The 1k resistor can be made a lot lower in value, speeding up the switching, but it'll then be dissipating more power (if 100 ohms it'll dissipate 1.44W).
The simplest alternative to the circuit is using a logic level FET in place of the IRF3205 - then the driver FET can be eliminated. You still have limited current to drive the gate (Arduino outputs absolute max is 40mA so the lowest value gate resistor you should use is 150 ohms)
For more demanding loads you can use a MOSFET driver chip like the MIC4422 between the Arduino and the power FET - you'll get much faster switching but you'll need good decoupling on the driver chip. A gate resistor of 10 ohms or less would then be sensible giving 100ns switching or so.