Bipolar emitter-coupled logic multiplexer

摘要

A high speed multiplexer circuit is described which includes a plurality of input bipolar transistors and a reference bipolar transistor. The input and reference transistors have their emitters commonly coupled to an emitter current supply and their collectors coupled to a collector supply. The collector of the reference transistor is coupled to the collector supply through an impedance. A reference potential is connected to the base of the reference bipolar transistor and biases it for conduction. An input signal to be multiplexed is connected to the base of each of the input bipolar transistors and a diode circuit is coupled between the base of each of the input bipolar transistors and a switch input. A switch input, in a first state, causes the diode circuit to conduct and clamp the base of an input transistor, to prevent it from responding to a signal input. The switch input also manifests a second state which renders the diode circuit non-conductive and enables an input transistor to conduct in response to an input signal. The conduction of an input transistor changes current flow through the reference transistor, which change is reflected across the collector connected impedance and sensed as an output.