Tri-state-capable driver circuit
AssigneeSiemens Aktiengesellschaft
InventorsJoerg Berthold, Gerhard Nebel, Doris Schmitt-Landsiedel
Life of this patent
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Abstract
A tri-state capable driver circuit or totem pole circuit is formed in BiCMOS technology and includes a selection circuit, first and second drive circuits, and first and second bipolar transistors. A short circuit unit is connected between the base and the emitter of the first bipolar transistor to prevent excessively high inhibit voltages across the base-emitter junction of the first bipolar transistor. The operation of the short circuit unit depends upon signals received at the tri-state activation input.
Claims9
A tri-state-capable driver circuit for connection to a supply voltage terminal and a reference potential terminal and a tri-state-activation input and to an input, comprising:
- a selection circuit connected to said supply voltage terminal and to said reference potential terminal and to said tri-state-activation input, said selection circuit having first and second outputs whereby said first output of said selection circuit carries a logical 1 and said second output of said selection circuit carries a logical 0 when a logical 1 is applied to said tri-state-activation input and whereby said first and second outputs of said selection circuit carry a signal that is an inverse of a signal at said input of the driver circuit when a logical 0 is applied to said tri-state-activation input;
- a first drive circuit connected to said supply voltage terminal and to said reference voltage terminal, said first drive circuit having a first input connected to said first output of the selection circuit, said first drive circuit having a second input connected to said second output of said selection circuit, said first drive circuit having an output at a high-impedance state when a logical 1 is applied to said first input of said first drive circuit and a logical 0 is simultaneously applied to said second input of said first drive circuit, and said output of said first drive circuit carrying a signal that is non-inverted in comparison to a signal at said input of said driver circuit when one of a logical 0 and a logical 1 is simultaneously adjacent at both inputs of said first drive circuit;
- a second drive circuit is connected to said supply voltage terminal and to said second output of said selection circuit, said second drive circuit having an output whereby said output of said second drive circuit has a logical 0 when a logical 1 is applied to said tri-state-activation input, and said output of said second drive circuit has a signal that is an inverse of a signal at said input of said driver circuit when a logical 0 is applied to said tri-state-activation input;
- a first bipolar transistor of a first type having base that is connected to said output of said first drive circuit and having a collector connected to said supply voltage terminal and having an emitter connected to an output of said driver circuit;
- a second bipolar transistor of said first type having a base connected to said output of said second drive circuit and having a collector connected to said output of said driver circuit and having an emitter connected to said reference potential terminal;
- a short-circuit means for shorting said base of said first bipolar transistor and said emitter of said first bipolar transistor when a logical 1 is applied to said tri-state-activation unit and for separating said base of said first bipolar transistor from said emitter of said first bipolar transistor when a logical 0 is applied to said tri-state-activation input.
Dependencies are inferred from the claim text.