US 4,746,817 A · BIFET logic circuit

Abstract

A BIFET logic circuit for quickly switching an output line from a high level to a reference level. The BICMOS circuit comprises a push-pull circuit including a first bipolar transistor for driving current into an output line, and a second bipolar transistor for sinking current from the output line; a CFET logic circuit for performing a logic function and including at least one N type FET for providing current to the base of the second bipolar transistor when a set of input lines to the CFET circuit has a first set of predetermined values; and a resistive means for connecting one of the source or drain of the at least one NFET to a power supply to provide a source of base current to the second bipolar transistor, even when the output line drops in voltage. This circuit is especially advantageous for driving low threshold CFET circuits. In a preferred embodiment, the circuit further includes a device for preventing a voltage differential of more than a predetermined amount between the base and emitter of the first bipolar transistor, to thereby ensure proper push-pull operation of the bipolar transistors.

Claims30

Dependent claims

A BIFET circuit, comprising:

at least one input line and an output line;
a CFET logic circuit having an input terminal connected to said at least one input line, said CFET logic circuit for generating different signals on a first and a second control lines in accordance with the signal values on said at least one input line;
a push-pull circuit connected to said first and second control lines and formed of bipolar transistors for driving current into said output line if said first control line is in a predetermined value range, and for sinking current from said output line if said second control line is in a predetermined value range;
a power supply;
and
resistive means for connecting said power supply to provide a current of a desired polarity through said CFET logic circuit to said second control line to thereby cause said push-pull circuit to sink current from said output line even after said output line drops in voltage.

3 more elements

A BIFET logic circuit, for quickly switching an output line from a high level to a low level comprising:

at least two input lines and an output line;
means for driving current into or sinking current out of said output line in accordance with the voltage values on said at least two input lines, said driving means including
a bipolar transistor operative, when conductive, to sink current from said output line;
at least one N type FET with its gate connected to one of said input lines for providing current therethrough to the base of said bipolar transistor when parameters of said at least two input lines have a first set of predetermined values;
a power supply;
means for initially providing current from said power supply to said at least one N type FET when said parameters of said at least two input lines have changed to said first set of predetermined values;
and
resistive means different from said at least one N type FET, in shunt with said current providing means, for connecting one of said source or drain of said at least one N type FET to said power supply to provide a source of base current through said at least one N type FET to said bipolar transistor even after said output line drops in voltage.

5 more elements

Dependencies are inferred from the claim text.

BIFET logic circuit

Life of this patent

BIFET logic circuit

Life of this patent

Abstract

Claims30