Interface receiver
AssigneeU.S. Philips Corporation
InventorDesmond Ross Armstrong
Life of this patent
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Abstract
A switching circuit is disclosed that is operative from a single supply voltage and is capable of switching in response to both positive and negative voltage input signals and exhibits hysteresis within defined positive and negative threshold voltage limits with respect to a datum voltage level. The circuit includes an input transistor having an input electrode connected to the signal input terminal and a transistor - diode current mirror connected to said input electrode whereby the current mirror defines one of the threshold voltage limits.
Claims17
A switching circuit adapted to switch states in response to both positive and negative voltage input signals and which exhibits a hysteresis characteristic within defined positive and negative threshold voltage limits with respect to ground voltage comprising, means for energizing said switching circuit from a single voltage supply applied between a ground voltage rail and a supply voltage rail, a signal input terminal for applying said positive and negative voltage input signals to the circuit, an input transistor having an input electrode connected to said signal input terminal, a transistor-diode current mirror having the collector of the current mirror transistor connected directly to the input electrode of the input transistor and the emitter of the current mirror transistor connected directly to the ground voltage rail, and means including said current mirror for defining one of the threshold voltage limits.
A switching circuit according to claim further comprising an auxiliary circuit coupled to the signal input terminal and the bistable circuit and including means for controlling the state of the bistable element if the input signal voltage remains near to the datum voltage level for a given time period.
A switching circuit that exhibits a hysteresis characteristic within defined positive and negative voltage threshold switching levels with respect to a reference voltage and adapted to switch states in response to positive and negative voltage input signals comprising, a source of supply voltage connected between a reference voltage terminal and supply voltage terminal, means coupling the switching circuit to said reference and supply voltage terminals, a signal input terminal, an input transistor having an input electrode connected to said signal input terminal and first and second electrodes coupled to the reference and supply voltage terminals, respectively, a current mirror device having first, second and third terminals, means connecting said first, second and third current mirror terminals to the input electrode of the input transistor, the reference voltage terminal and to a voltage control terminal which supplies a voltage that is independent of the voltage at said signal input terminal, respectively, so that the current mirror device defines one of said voltage threshold levels.
Dependencies are inferred from the claim text.