>HI,PICLISTERS,
>                Five days ago a sent an e-mail asking for an H-Bridge
>for a DC 1/8 hp 220 volt motor.Thanks for all the answers.I beleive I've
>learnt something on MOSFETS through this thread.
>         I finally used a couple of relay switches and a IRP350
> mosfet doing the PWM at 10 khz with its source connected to ground.This
> works just fine,since I only need to invert the motor every one or two
> seconds.Besides, the relays also give me the advantage of a simple but
effective brake,by shortcircuiting the motor and connecting both terminals
to ground.
>                 Anyhow,I would like to learn how to drive the high side
> bridge for a high voltage application like 400 volts,since I am
> interested in three phase inductive motors also,and I'm going to need a full
> 6 mosfet (or IGBT) bridge with the upper 3 sourced to 380 volts,and the
lower 3
> sourced to ground performing PWM.
>                 Can you send me some schematics on how to drive those upper
> mosfets?.I just can't figure out how to pump all that voltage (400V) into
> the upper mosfet gate(I need 12 volts drop between gate and source).If
> optocouplers can't do the job,then what can I use to interface the 16c74
> with the upper bridge?I've read something about a bootstrap,what's that?
>
>                 Thanks in advance,
>
> Walter Markiw.
>
>