The astable multivibrator
A multivibrator circuit containing resistors is a basic memory element. But the two transistor switches in such a circuit can also be linked by capacitors. Their behaviour will be different because the current through a capacitor is not constant. As the plates
of the capacitor become charged, the potential difference between them increases. This voltage opposes further flow of charge, so the current decreases. The result of this is that the circuit switches continually from one state to the other, and is thus referred to as an astable.