HIGH SPEED BICMOS LOGIC CIRCUIT

摘要

A signal applied through a signal input terminal is logically processed by a logic circuit such as a CMOS inverter and the processed signal is supplied from the signal output terminal. A pinch resistor has a resistance value controlled in accordance with a variation of a voltage at the signal output terminal. Specifically, the pinch resistor has a higher resistance value at an initial stage in the switching operation in which an output from the logic circuit lowers from a logical high level to a logical low level, and supplies a large base current to a bipolar transistor. At a later stage in the switching operation, the pinch resistor has a small resistance value, so that a residual charge in the signal output terminal and a base charge in the bipolar transistor are rapidly emitted through the pinch resistor. Thus, the resistance value of the pinch resistor is always maintained at an optimum value, which increases a speed of the switching operation of the logic circuit.