I would like to have a precision current source ~1 μA loaded by a resistor ~100k and a voltage source. Also I would like to switch on and off the current. The problem is that when the transistor switch turns off, since the current is very small, it has a trouble dissipating the charge collected in the channel in the case of a MOSFET or in the base in the case of a BJT. As the result switching off time is very slow. Is there a quick solution?
Upd. I need to switch off the current, not just shunt it to the ground.