can turn on 1 FET but not another
can turn on 1 FET but not another
(OP)
I have two FETs I am trying to turn on - IR620 and IR 3215, both N-channel FETs. VDD = 9v, gate signal is 40KHz +5V. The International Rectifier IR3415 N-channel was turned on with a TC428 FET driver no problem outputting a nice sqaure wave. It was also turned on with 6 parallel 74A0C inverters. Ok, no problem. Then I tried turning on the IR620 - it did not turn on first with either the inverter or FET driver scenario. I made a voltage doubler from one TC428 (in spec sheet) and used its output to feed VDD of another TC428 and hence, doubled my gate voltage. The IR620 still did not turn on. I increased VDD to the first TC428 to 9v doubling to 18v, and it gave a partial, sloppy, non-sqaure 40KHz signal.
Is the RDS(On) the culprit? =.018 for the 3415 and .8 for the 620.
Spec sheets are here:
http://ww w.irf.com/ product-in fo/datashe ets/data/i rf3415.pdf
http://w ww.irf.com /product-i nfo/datash eets/data/ irf620.pdf
Is the RDS(On) the culprit? =.018 for the 3415 and .8 for the 620.
Spec sheets are here:
http://ww
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RE: can turn on 1 FET but not another
RE: can turn on 1 FET but not another
RE: can turn on 1 FET but not another
TTFN
RE: can turn on 1 FET but not another
The only situation where channel resistance would have a say is if you load the output. You haven't said if you run lightly or heavily loaded. And if you have capacitors in the load. Do you?
Gunnar Englund
www.gke.org
RE: can turn on 1 FET but not another
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: can turn on 1 FET but not another
RE: can turn on 1 FET but not another
http:
RE: can turn on 1 FET but not another
1: With this kind of setup, you have absolutely no control over turn-on and turn-off times. I strongly suggest that you have a problem with "shoot-through" (but FETs on at the same time.)
2: 1N4001 at 40 kHz? Think again.
I'd strongly advise you to use a deidcated driver like ON NCP5181 or IR IRC2114, there is a reason they've been made.
Benta.
RE: can turn on 1 FET but not another
According to your schematic, the source of the IRF9530 is connected to the drain of the N channel, which will turn on the body diode of the P channel thus connecting the drain of the N channel directly to the power rail...
RE: can turn on 1 FET but not another
Replacing the P channel 9630 with an IRF9640 and the circuit above began working (bad FET?). I used a 9v battery test source for the push-pull network and the output is a 9Vpp 40.00KHz square wave. FYI, once the FET was changed, the voltage doubler was unnecessary and was driven soley with the TC428 at +5V.
My new problem is when I change the 9v source for the network to 100V DC HV converter (EMCO Q0-05) no square output. Is this more likely a problem with my converter or shoot through.
http://www.emcohighvoltage.com/
go to "Q series"
Thanks
corrected: http:
RE: can turn on 1 FET but not another
Your power supply only puts out maybe 2.5 mA? That means you can't drive a load larger than about 150 pF. Your transistors' drain capacitances alone probably exceed that value.
TTFN
RE: can turn on 1 FET but not another