Differential amplifier having increased bandwidth

Claim 2

A differential amplifier comprising first and second input terminals, first and second transistors of NPN type having bases connected respectively to said first and second input terminals, the collectors of said first and second transistors being connected respectively through first and second load impedances to one terminal of a power supply, third and fourth transistors of PNP type having bases connected to a first constant-current source, the collectors of said third and fourth transistors being connected respective through third and fourth load impedances to the other terminal of said power supply, the emitters of said third and fourth transistors being connected respectively to the emitters of said first and second transistors, fifth and sixth transistors of NPN type having collectors connected respectively to the collectors of said first and second transistors, the bases of said fifth and sixth transistors being connected respectively to the emitters of said first and second transistors, a second constant-current source connected to the emitters of said fifth and sixth transistors, first output signal deriving means connected to the collector of one of said first and second transistors, and second output signal deriving means connected to the collector of one of said third and fourth transistors, whereby a high-frequency component of an amplified signal applied to said first and second input terminAls is derived from said first output signal deriving means, and a low-frequency component of the amplified signal is derived from said second output signal deriving means.

Claim 3

The differential amplifier as claimed in claim 1, wherein said third and said fourth transistors are each made of a transistor having a collector region and an emitter region disposed laterally thereto.

Claim 4

The differential amplifier as claimed in claim 1, which is fabricated in the form of an integrated circuit device.

Claim 5

The differential amplifier of claim 1, further comprising seventh and eighth transistors of NPN type, the bases of said seventh and eighth transistors being connected respectively to said first and second output signal deriving means, the collectors of said seventh and eighth transistors being connected to said one terminal of said power supply, the emitter of said eighth transistor being connected through a sixth load impedance to the other terminal of said power supply, a ninth transistor of NPN type having a collector connected through a fifth load impedance to the emitter of said seventh transistor, the base of said ninth transistor being connected to said emitter of said eighth transistor, the emitter of said ninth transistor being connected to the other terminal of said power supply, and an output terminal connected to said collector of said ninth transistor, whereby the high-frequency component of the amplified signal derived from said first output signal deriving means is further amplified by said seventh transistor and sent to said output terminal, the low-frequency component of the amplified signal derived from said second output signal deriving means being further amplified by said eighth and ninth transistors and sent to said output terminal, and the high-frequency component and the low-frequency component of the further amplified signal being superposed at and derived from said output terminal.

Claim 6

The differential amplifier of claim 1, further comprising third output signal deriving means connected to the other of the collectors of said first and second transistors and producing a high-frequency component of the amplified signal, an output terminal, seventh and eighth transistors of NPN type having bases connected respectively to said first and third output signal deriving means, the collectors of said seventh and eighth transistors being connected to said one terminal of said power supply, the emitters of said seventh and eighth transistors being connected respectively through fifth and sixth load impedances and third and fourth constant-current sources to said other terminal of said power supply, a ninth transistor having a base connected to said second output signal deriving means, the collector of said ninth transistor being connected to said one terminal of said power supply, the emitter of said ninth transistor being connected through a seventh load impedance to said other terminal of said power supply, tenth and eleventh transistors of NPN type having bases connected respectively to the junction of said third and fourth constant-current sources and said fifth and sixth load impedances, the collector of said tenth transistor being connected to said output terminal and through an eighth load impedance to said one terminal of said power supply, the collector of said eleventh transistor being connected directly to said one terminal of said power supply, and a twelfth transistor of NPN type having a base connected to the emitter of said ninth transistor, the collector of said twelfth transistor being connected to the emitters of said tenth and eleventh transistors, the emitter of said twelfth transistor being connected to said other terminal of said power supply, whereby the high-frequency component of the amplified signal derived from said first and third output signal deriving means is further amplified by said seventh, eighth, tenth and eleventh transistors, the low-frequency component of the amplified signal derived from said second output signAl deriving means is further amplified by said ninth and twelfth transistors, and the further amplified high-frequency component and the further amplified low-frequency component are superimposed at and derived from said output terminal.