Patent ID: 6542009
Filing Date: 2003-04-01
Classification: H03K

Abstract:
A signal hold circuit comprising:a comparison circuit that compares an input signal with an output signal and outputs a comparison signal, a capacitor for generating the output signal, a first constant current circuit for supplying a first current to the capacitor, a second constant current circuit for supplying a second current with the opposite polarity to that of the first current to the capacitor, a third constant current circuit for supplying a third current with the opposite polarity to that of the first current to the capacitor, a first switch element that is electrically connected between the capacitor and the first constant current circuit and is turned on corresponding to the comparison signal, a rectifying element that is electrically connected between the first switch element and the capacitor, a second switch element that is connected between the capacitor and the third constant current circuit, and a control circuit that uses the comparison signal as its input and outputs a control signal for closing the second switch element when the comparison signal does not change during a prescribed amount of time.