| 摘要 |
A technique and circuit for switching a bipolar output stage between an active mode in which the stage operates as a voltage source and an inhibit mode in which the stage is deactivated and the output node presents a floating high-impedance. The output stage may be in a digital device such as a digital pin driver circuit, or in an analog amplifier. Considering first the digital application, in the active mode, a digital output is switched between logic high and logic low voltages established by external references. The logic high and logic low reference voltages, and the corresponding output voltages, may be set to zero, a positive voltage or a negative voltage independently of each other; a logic "one" can thus be set to a voltage below a logic "zero". When the output stage is an analog amplifier, in active mode it amplifies its input signal. In either arrangement, in the "inhibit mode", the output stage transistors are turned off by reverse-biasing their base-emitter junctions relative to the output node of the circuit, to provide a floating high-impedance output node. In the inhibit mode, additional means are provided for substantially cancelling leakage current at the output node.
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