Regulated substrate bias generator for random access memory

Abstract

An improved substrate bias generator is disclosed for use in a capacitive charge storage integrated circuit memory device having an external voltage supply. The generator comprises means for generating first and second timing signals, charge pumping means disposed for pumping positive charge from the substrate of the integrated circuit memory device in response to the first and second timing signals. Removal of the positive charge from the substrate polarizes the substrate at a negative potential, which is the generated bias voltage. A voltage regulation means is disposed between the output of the charge pumping means (i.e., the substrate) and the means for generating the timing signals. The voltage regulation means provides a reference potential that regulates the amount of charge pumped from the substrate as a function of the magnitude of the generated bias voltage. The voltage regulation means includes a voltage clamp circuit that is disposed for clamping the generated bias voltage to a limited negative value; a modulator circuit means disposed at the output of the voltage regulation means; and, a generator circuit means disposed at the output of the modulator circuit means for supplying the reference potential in response to the output voltage from the clamp circuit means as modified by the modulator circuit means.