Bootstrapped level shift interface circuit with fast rise and fall times

Abstract

An input circuit for a field effect transistor (FET) storage is described which consists of a bootstrap inverter which by a dynamically operating charge-up circuit is supplemented for charging up the bootstrap node to the full operating voltage, and which can be directly controlled with TTL levels without a level converter consisting of bipolar transistors being inserted. For that purpose, the input electrode of the bootstrap capacitor of the dynamically operating charge-up circuit is connected to the output of an inverter following the input circuit. Furthermore a discharge branch is provided for the node of the dynamically operating charge-up circuit. With its other end, together with the gate of the charge-up field effect transistor of the dynamic charge-up circuit, the discharge branch is connected to the output of another inverter following the first one. It is thus assured that when owing to the bootstrap effect the potential of the bootstrap node rises over the value VH of the operating voltage, this node cannot be discharged via the FET's in the charge-up circuit to the positive pole of the operating voltage source. This would counteract the rise of the potential of the bootstrap node so that the potential and the output of the input circuit would rise only slowly, and would not reach the full value VH of the operating voltage.