help design a "memory circuit"

Thread Starter


Joined Sep 19, 2006
I need to design an analog circuit with the following caractaristics:

1) Input voltage: V, variable.
2) When V>0, a capacitor charges until it reaches a maximum.
3) When V<0, the capacitor discharges, until it reaches a minimum.
4) When V=0, the capacitor charge remains unchanged.
5) it should be as simple as possible, use only discrete components (or 741 op amp).
6) it doesn't need to be very precise, but when V=0 the capacitor must not change!
7) the capacitor is about 1uF, not electrolytic.

I thought of using a voltage controlled current source for this, but every current source I use has too high gain (greater than 1 mA/V). Anyone could help me?


Joined Apr 20, 2004

Putting a charge on a capacitor isn't really a memory device - at least not since the A-6 attack computer got upgraded in 1970-something. That's almost as old as Johnson tubes.

Applying the voltage through a resistor will give you a controlled rate of charge. Using a toggle switch to ground the capacitor will hold the cap at zero quite effectively.