High-speed and low-power consumption decoder unit implemented by emitter-coupled logic circuit

摘要

A decoder circuit is implemented by emitter coupled logic circuits, and comprises decoding stages (31 to 3n) respectively supplied with combinations of component bits, driver stages (41 to 4n) respectively associated with the decoding stages for driving capacitive loads (CP1 to CPn), and bypassing circuits (51 to 5n) coupled between the output terminals (OUT1 to OUTn) of the driver stages and a common constant current source (60), wherein each of the bypassing circuits is implemented by a bipolar transistor (Qb1 to Qbn) having a collector to emitter current path between the associated output terminal and the common constant current source and a base node coupled through a resistive element (R11 to R1n) with the associated output terminal so that discharge current flows through the collector to emitter current path until all the electric charges are evacuated from the capacitive load, thereby increasing operation speed.