Hi Dick, it is not really all that necessary to use that chip. It is quite
possible to drive the gates quite adequately with a PNP-NPN totem pair
(emitter followers...the emitters to the output ...npn top pnp
bottom...bases strapped together). These can be driven from 12v logic levels
(cmos) Most switching FETs will turn on at about 6 volts but need around 10
to 12 volts for high currents. In fact the chipp can be a cause of FET
failure, it you remove the drive from the TC44xx and dont kill the supply
the output just stays high, holding the FET on. I think there are some
advantages in the keying technique used by Dave G3YXM and Dave G0MRF, in
that as the supply is keyed the "ON" times changes "gently" helping tame the
click.
Cheers de Alan G3NYK
alan.melia@btinternet.com
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