Integrator "instantaneous" reset

[RiskCord]

Hi friends

As part of a class d amplifier I need to implement an integrator which has to be reseted, ideally, instantaneously. Here I post my idea... I thought the best option would be to use an analog switch. Fairchild, MAxim, Intersil offer very nice (very fast) switches but they are intended for digital level signals, i.e. not much more than 5 volts. As the level of voltage which I want to reset may go slightly higher than 10 volts, they doesnt seem to be useful. So, my idea was to use two MOSFETs in antiseries.
As it is shown on the picture, under ideal conditions the integrator integrates in only once sense, i.e. voltage over the cap is negative, returns to zero when it is reseted and then goes negative again. However, in actual operation it might go positive. That's why I can't use a single MOSFET as the internal body diode would clamp the positive voltage. The 20 ns pulse is only figurative as I suppose its far too optimistic. Anyway, ideas, suggestions and critics are very welcome.
Thanks!

Pablo

[gootee]

Hi Pablo,

I haven't analyzed your circuit idea. But the IC manufacturers' Application Notes contain quite a few rather-ingenious integrator resetting schemes. Do some searches among the appnotes at linear.com, analog.com, national.com, maxim-ic.com, and the others. You might also find some applicable ideas in some older sample-and-hold-related appnotes.

You might also want to download the free LTspice (aka Switchercad) simulation software, from linear.com, with which you should be able to evaluate different reset-circuit schemes.