Differential amplifier

Claim 2

A differential amplifier comprising: a pair of amplifier stages each having input, common and output electrodes and a load circuit coupled to said output electrodes, said load circuit comprising: first and second transistors each having base, emitter and collector electrodes; means connecting said emitter electrodes in common to a source of operating potential; means coupled between said base and emitter electrodes of said transistors for providing equal voltages between said base and emitter electrodes of both transistors; means for coupling said collector electrodes one to each of said output electrodes; and common mode coupling means connected between said output electrodes and said base electrodes including a pair of semiconductor junction devices each providing a current versus voltage coupling characteristic wherein voltage across each said device is equal to or greater than a threshold value for a relatively wide range of current values.

Claim 3

A differential amplifier as defined in claim 1 wherein: said pair of semiconductor devices comprise third and fourth transistors having a base to emitter current versus voltage characteristic wherein said voltage is equal to or exceeds a threshold value for a relatively wide range of current values.

Claim 4

A differentiaL amplifier as defined in claim 2 wherein: said third and fourth transistors have emitter electrodes coupled in common to said base electrodes of said first and second transistors and base electrodes each coupled to said output electrodes of said amplifier stages, and have collector electrodes providing output terminals for coupling to an output circuit.

Claim 5

A differential amplifier as defined in claim 2 wherein: a diode is connected directly between and is poled for forward conduction in the same direction as said base and emitter electrodes of said first transistor.

Claim 6

A differential amplifier as defined in claim 1 wherein: said pair of amplifier stages each include: a cascode connected pair of transistors having common electrodes and wherein the amplifier stages have a common bias circuit comprising a pair of series connected diodes connected between the common electrodes of the cascode connected transistors.

Claim 7

A differential amplifier as defined in claim 5 wherein: one of said transistors in each of said cascode connected pair of transistors has an extremely low collector to emitter breakdown voltage and is characterized by extremely high beta current gain.

Claim 8

A differential amplifier as defined in claim 6 wherein: one of said diodes in said common bias circuit is a transistor having matched electrical characteristics to said high beta gain transistors which is connected as a diode.

Claim 9

An amplifier comprising first and second transistors each having base, emitter and collector electrodes; means providing a current source connected between the emitter electrodes of said first and second transistors and a first terminal; third and fourth transistors each including emitter, collector and base electrodes; means connecting the collector electrodes of said first and third transistors; means connecting the collector electrodes of said second and fourth transistors; means connecting the base electrodes of said third and fourth transistors; means connecting the emitter electrodes of said third and fourth transistors in common to a second terminal; fifth and sixth transistors each including base, emitter and collector electrodes; means connecting the emitter electrodes of said fifth and sixth transistors in common to the base electrodes of said third and fourth transistors; means connecting the base electrode of said fifth transistor to the collector electrode of said third transistor for maintaining the voltage drop between the base and emitter electrodes of said fifth transistor and the collector-to-base voltage of said third transistor substantially equal; means connecting the base electrode of said sixth transistor to the collector electrode of said fourth transistor for maintaining the voltage drop between the base and emitter electrodes of said sixth transistor and the collector-to-base voltage of said fourth transistor substantially equal; means providing first and second signal input terminals connected to the base electrodes of said first and second transistors respectively; and output circuit means for connection to the collector electrodes of said fifth and sixth transistors.

Claim 10

An amplifier comprising first and second transistors each having base, emitter and collector electrodes; means providing a current source connected between the emitter electrodes of said first and second transistors and a first terminal; third and fourth transistors each including emitter, collector and base electrodes; means connecting the collector electrodes of said first and third transistors; means connecting the collector electrodes of said second and fourth transistors; means connecting the base electrodes of said third and fourth transistors; means connecting the emitter electrodes of said third and fourth transistors in common to a second terminal; fifth and sixth transistors each including base, emitter and collector electrodes; means connecting the emitter electrodes of said fifth and sixth transistors in common to the base electrodes of said third and fourth transistors; means connecting the base electrode of said fifth transistor to the collector electrode of said third transistor for maintaining the voltage drop between the base and emitter electrodes of said fifth transistor and the collector-to-base voltage of said third transistor substantially equal; means connecting the base electrode of said sixth transistor to the collector electrode of said fourth transistor for maintaining the voltage drop between the base and emitter electrodes of said sixth transistor and the collector-to-base voltage of said fourth transistor substantially equal; means providing first and second signal input terminals connected to the base electrodes of said first and second transistors respectively; and output circuit means for connection to the collector electrodes of said fifth and sixth transistors.

Claim 11

An amplifier as defined in claim 8 wherein said output circuit means includes a seventh transistor including base, emitter and collector electrodes; means connecting the collector electrodes of said sixth and seventh transistors for providing a single-ended signal output terminal; means connecting the base electrode of said seventh transistor to the collector electrode of said fifth transistor; an eighth transistor having base and collector electrodes connected in common to said base electrode of said seventh transistor and an emitter electrode connected to said emitter electrode of said seventh transistor; and means connecting the emitter electrode of said seventh transistor to said first terminal.

Claim 12

A differential amplifier according to claim 4 Wherein: conduction characteristics of said diode and said first and second transistors are proportionally related.

Claim 13

A differential amplifier according to claim 9 and further comprising: a ninth transistor having base and collector electrodes connected in common to said base electrodes of said third and fourth transistors and an emitter electrode connected to said second terminal, conduction characteristics of said third, fourth and ninth transistor being proportionally related.

Claim 14

A differential amplifier according to claim 11 wherein: said first, second, seventh and eighth transistors are of one type conductivity and said third, fourth, fifth, sixth and ninth transistors are of a second type conductivity.

Claim 15

An amplifier comprising: first and second transistors of a first type conductivity each having base, emitter and collector electrodes; means for providing a source of current connected between a first supply terminal and said emitter electrodes of said first and second transistors; first and second active device load circuits connected between a second supply terminal and said collector electrodes of said first and second transistors, respectively; each said load circuit comprising a diode-connected transistor and a further transistor, said diode-connected and further transistors having proportionally related conduction characteristics and being of a second type conductivity; signal combining means comprising a diode-connected transistor, having collector and base electrodes connected together and an emitter electrode direct current coupled to a second supply terminal, and an output transistor having base and emitter electrodes connected to corresponding electrodes of said last-named diode-connected transistor and a collector electrode connected to a single-ended output terminal, said last-mentioned transistor and diode-connected transistor having proportionally related conduction characteristics and being of said first type conductivity; each of said load circuits having a collector output electrode, said collector output electrode of said first load circuit being connected to said base electrode of said output transistor and said collector output electrode of said second load circuit being connected to said single-ended output terminal.

Claim 16

An amplifier comprising: first and second transistors of a first type conductivity each having base, emitter and collector electrodes; means for providing a source of current connected between a first supply terminal and said emitter electrodes of said first and second transistors; first and second active device load circuits connected between a second supply terminal and said collector electrodes of said first and second transistors, respectively; each said load circuit comprising a diode-connected transistor and a further transistor, said diode-connected and further transistors having proportionally related conduction characteristics and being of a second type conductivity; signal combining means comprising a diode-connected transistor, having collector and base electrodes connected together and an emitter electrode direct current coupled to a second supply terminal, and an output transistor having base and emitter electrodes connected to corresponding electrodes of said last-named diode-connected transistor and a collector electrode connected to a single-ended output terminal, said last-mentioned transistor and diode-connected transistor having proportionally related conduction characteristics and being of said first type conductivity; each of said load circuits having a collector output electrode, said collector output electrode of said first load circuit being connected to said base electrode of said output transistor and said collector output electrode of said second load circuit being connected to said single-ended output terminal.

Claim 17

An amplifier according to claim 13 and further comprising: first and second sources of voltage connected, respectively, to said first and second supply terminals, and means coupled to said base electrodes of said first and second transistors for supplying input signals referenced to a voltage substantially midway between voltages of said sources.

Claim 18

An amplifier according to claim 14 wherein: said means for providing a source of current comprises a diode-connected transistor and a current source transistor having proportionally related conduction characteristics and being of said first type conductivity for providing to the joined emitter electrodes of said first and second transistors a current proportional to a control current supplied to said diode-connected transistor.

Claim 19

An amplifier according to claim 15 wherein: said first and second sources of voltage provide substantially equal voltages of opposite polarity with respect to a common reference.

Claim 20

An amplifier according to claim 16 wherein: said first type conductivity corresponds to NPN transistors and said second type conductivity corresponds to PNP transistors, and said first and second voltage sources are, respectively, of negative and positive polarity.