Differential amplifier

Claim 2

In a differential amplifier circuit having: first and second transistors, each having a base, an emitter, and a collector; first and second input terminals connected to couple first and second input signals to the bases of said first and second transistors, respectively; a first constant current source connected to the emitters of each of said transistors; a power supply terminal to which a supply voltage for said amplifier is applied; output means, connected to the collectors of said first and second transistors for providing an output signal representative of the amplified difference of said first and second signals applied to said first and second input terminals; and means for coupling the supply voltage applied to said power supply terminal to said first and second transistors; the improvement comprising: means, connected to said coupling means, for attenuating an alternating current component of the supply voltage applied to said power supply terminal, and substantially preventing said alternating current component of said supply voltage from being supplied to said first and second transistors, comprising a third transistor having a base, an emitter and a collector, the collector of which is connected to said power supply terminal and the emitter of which is resistively coupled to the collectors of said first and second transistors, with a resistor being connected between the collector and base of said third transistor and a capacitor being connected between the base of said third transistor and a reference potential terminal.

Claim 3

A differential amplifier circuit according to claim 1, wherein the product of the resistance value R of said resistor and the capacitance value of C of said capacitor satisfied the relationship RC >> 1/2 pi f, where f is the fluctuating frequency of the voltage applied to said power supply terminal.

Claim 4

In a differential amplifier circuit having: first and second transistors, each having a base, an emitter, and a collector; first and second input terminals connected to couple first and second input signals to the bases of said first and second transistors, respectively; a first constant current source connected to the emitters of each of said transistors; a power supply terminal to which a supply voltage for said amplifier is applied; output means, connected to the collectors of said first and second transistors for providing an output signal representative of the amplified difference of said first and second signals applied to said first and second input terminals; and means for coupling the supply voltage applied to said power supply terminal to said first and second transistors; the improvement comprising: means, connected to said coupling means, for attenuating an alternating current component of the supply voltage applied to said power supply terminal, and substantially preventing said alternating current component of said supply voltage from being supplied to said first and second transistors, comprising a third transistor having a base, an emitter, and a collector, the collector of which is connected to said power supply terminal and the emitter of which is resistively coupled to the collectors of said first and second transistors, with a resistor being connected between the collector and base of said third transistor and further including a diode circuit and a capacitor connected in series between the base of said third transistor and a reference potential terminal.

Claim 5

In a differential amplifier circuit having: first and second transistors, each having a base, an emitter, and a collector; first and second input terminals connected to couple first and second input signals to the bases of said first and second transistors, respectively; a first constant current source connected to the emitters of each of said transistors; a power supply terminal to which a supply voltage for said amplifier is applied; output means, connected to the collectors of said first and second transistors for providing an output signal representative of the amplified difference of said first and second signals applied to said first and second input terminals; and means for coupling the supply voltage applied to said power supply terminal to said first and second transistors; the improvement comprising: means, connected to said coupling means, for attenuating an alternating current component of the supply voltage applied to said power supply terminal, and substantially preventing said alternating current component of said supply voltage from being supplied to said first and second transistors, comprising a third transistor having a base, an emitter, and a collector, the collector of which is connected to said power supply terminal and the emitter of which is resistively coupled to the collectors of said first and second transistors, with a resistor being connected between the collector and base of said third transistor and further including a diode circuit and a capacitor connected in series between the base of said third transistor and a reference potential terminal.

Claim 6

A differential amplifier circuit according to claim 3, wherein the junction of said diode circuit and said capacitor iS coupled to the base of one of said first and second transistors.

Claim 7

In a differential amplifier circuit having: first and second transistors, each having a base, an emitter, and a collector; first and second input terminals connected to couple first and second input signals to the bases of said first and second transistors, respectively; a first constant current source connected to the emitters of each of said transistors; a power supply terminal to which a supply voltage for said amplifier is applied; output means, connected to the collectors of said first and second transistors for providing an output signal representative of the amplified difference of said first and second signals applied to said first and second input terminals; and means for coupling the supply voltage applied to said power supply terminal to said first and second transistors; the improvement comprising: ripple filter means including a first resistor connected between the power supply and respective load resistors coupled to the collectors of said first and second transistors of the differential amplifier; a second resistor one terminal of which is connected to the power supply; a diode circuit of at least one diode connected between the other terminal of said second resistor and the connection point of said first resistor and the load resistors, so that said diode circuit is forward-biased; and a capacitor connected between the other terminal of said second resistor and a common reference potential.

Claim 8

In a differential amplifier circuit having: first and second transistors, each having a base, an emitter, and a collector; first and second input terminals connected to couple first and second input signals to the bases of said first and second transistors, respectively; a first constant current source connected to the emitters of each of said transistors; a power supply terminal to which a supply voltage for said amplifier is applied; output means, connected to the collectors of said first and second transistors for providing an output signal representative of the amplified difference of said first and second signals applied to said first and second input terminals; and means for coupling the supply voltage applied to said power supply terminal to said first and second transistors; the improvement comprising: ripple filter means including a first resistor connected between the power supply and respective load resistors coupled to the collectors of said first and second transistors of the differential amplifier; a second resistor one terminal of which is connected to the power supply; a diode circuit of at least one diode connected between the other terminal of said second resistor and the connection point of said first resistor and the load resistors, so that said diode circuit is forward-biased; and a capacitor connected between the other terminal of said second resistor and a common reference potential.