TTL CURRENT SINKING CIRCUIT WITH TRANSIENT PERFORMANCE ENHANCEMENT DURING OUTPUT TRANSITION FROM HIGH TO LOW

摘要

Attorney Docket No.: 53.1139ABSTRACTTTL CURRENT SINKING CIRCUIT WITH TRANSIENT PERFORMANCEENHANCEMENT DURING OUTPUT TRANSITION FROM HIGH TO LOWA transient voltage difference circuit is coupledinto a TTL current sinking output circuit for transientperformance enhancement during transition from high to lowlevel potential at the output. The TT1 output circuitincludes a pulldown transistor element for sinking currentfrom an output node to low potential, a base drivetransistor for driving the base of a current sinkingpulldown transistor element, an input base node of the basedrive transistor coupled to receive input signals of highand low level potential, and a voltage clamp networkcoupled between the input base node and low potential formaintaining a potential level at the input base nodesufficient to turn on the base drive transistor. An RCnetwork is coupled between the input base node and lowpotential. The resistance of the RC network is coupled inseries with the voltage clamping network adding a transientoverdrive voltage in series with the clamping voltage atthe input base node when the capacitance of the RC networkis charging through the resistance during transition fromlow to high level potential at the input. The RC networkand the voltage clamp network effectively form a Y networkwith the common branch coupled to the input base nodethrough the resistance.