On the low FET, the 10k pullup to 12V to turn it on is way too high - not
sure if this would effect the high side FET but it will create problems
 of its own.
I'd start with 100 ohms but be prepared to drop it if you need fast turn
for PWM frequencies greater than a kHz or so. Possibly even lower.

What frequency are you testing at? you could be getting all sorts of miller
capacitance effects with the higher impedances in the circuit (upper and
lower FETs).

Make sure you have good decoulpling on your "+V" line also - as close as
reasonable to the FETs.

RP

On 3 February 2015 at 23:50, RussellMc <apptechnz@gmail.com> wrote:

> More comment needed but:
>
> High side FET is underdriven by 220R at other than near DC.
>
> N Channel high side gate drive must be above +V by Vgsth + some.
> Depends on FETS.
>
> High side pull down of 10k is much much too high.
> Add reverse diode across BC847 be junction so driver pills gate down BUT
> then watch gate -ve voltage - zener acting as forward diode will clamp
> this, but slowly.
>
> Overall I'm afraid that this cct needs enough work that copying something
> else that is known working may be easier.
>
> BUT persist if you wish and we can journey with you.
>
>
>           R
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