S&H

[Paul Maddox]

Magnus/Grant/all,

> A FET works by "pinching off" the channel by applying a highly negative
> voltage. Use a 1 meg resistor from the source to the gate. Then use an
> op-amp as a comparator with a diode on the output to pull the gate to -15
> volts for the "off" state. So "on" = floating "off" = -15 volts
> 

Thanks this was the problem, I had my voltage round the wrong way.. <DOH>

Paul