Importance

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Abstract

An I/O circuit is provided having a terminal for either receiving an input signal or providing an output signal. In one form, the circuit may be utilized in a system with multiple I/O circuits coupled via a two-wire interconnection having a common ground conductor throughout the system. Input signal levels are sensed within a narrow voltage range referenced, in part, to the V.sub.be of a bipolar transistor and independent of the power supply voltage of other interconnected circuits. In response to an enable signal, a differential amplifier provides an output drive signal proportional to the difference between the signal at the terminal and a reference voltage. The output drive signal is coupled to a driver stage which provides a predetermined limited current at the terminal, thereby providing an output signal. A voltage limiter allows the circuit to use bipolar transistors in a P-well CMOS process and to receive input voltages greater than the supply voltage of the circuit.

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First Claim