Signetics

North American Philips Corp, Signetics Division

Yong-In Shin

Thomas D Fletcher

A select buffer circuit includes a first inverter circuit, a second inverter circuit connected to the first, and a circuit for charging and discharging the base of an inverter transistor in the second inverter circuit from a node in the first inverter circuit. The charging and discharging circuit includes a Schottky diode connected to the inverter transistor, a Schottky transistor connected in series with the diode, and a resistor for coupling the base of the Schottky transistor to the node in the first inverter circuit. A bipolar multiplexer including the select buffer circuit offers the advantage of an improved output waveform.

Bipolar multiplexer having a select buffer circuit with a charging and

A switching device (22) responsive to an input voltage V.sub.A is powered by low and high internal supply voltages V.sub.L and V.sub.H. The device changes state as V.sub.A -V.sub.L passes a threshold voltage V.sub.T. After the device makes a desired change of state in response to rising V.sub.A, a hysteresis circuit (24) temporarily decreases V.sub.T below that which would otherwise be present. Likewise, after the device makes a desired change of state in the opposite direction when V.sub.A is falling, the hysteresis circuit temporarily decreases V.sub.T. In both cases, V.sub.T later automatically returns to its original value. This dynamic hysteresis prevents spikes in V.sub.L and V.sub.H from causing undesired changes in state.

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Orem, UT, United States of America

Yong-In Shin