Re: transistors instead of diodes?

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Malcolm Watts" <m.j.watts@xxxxxxxxxxxx>

On 23 Mar 2005, at 8:38, Tesla list wrote:

> Original poster: "Jolyon Cox" <jolyon@xxxxxxxxxxxxxxxxxxxxxxxx>
>
> I am wondering if in place of fast-recovery diode it would be possible
> to use a second transistor in anti-parallel with each transistor of
> the H-bridge; the latter switching on at the same time as the former
> but switching off a short period later to allow any spikes to be
> returned to the supply rails. Does anyone have any experience of doing
> this?

Some questions:

What type of transistors? If you are meaning MOSFETs, you might want
to consider what the substrate diode does. If you mean bipolars, you
might want to consider how they would react to having a large reverse
voltage placed across them. You might also want to consider how you
are going to drive an extra bundle of bases/gates. Is it worth the
hassle and cost? Finally, you might want to consider the consequences
of conduction timing being incorrect.

Malcolm