Back to results
US 4,380,740 AGranted
Current amplifier
AssigneeRCA Corporation
InventorLeonard A. Kaplan
Life of this patent
Estimating the term…
Abstract
A current amplifier having a gain factor substantially independent of the common emitter forward current gain (beta) of its component transistors uses a cascade arrangement of current mirror amplifiers (CMA's) to compensate for variations in beta. The output of a first CMA, which current transfer ratio thereof decreases as beta decreases, is connected to the input of a second CMA, which current transfer ratio thereof increases as beta decreases. The composite current gain of the combined first and second CMA's therefore tends to remain constant as the respective betas vary.
Claims10
A current amplifier having input and output terminals comprising:
- a first current mirror amplifier having input and output electrodes, the input electrode thereof being connected to said input terminal;
- a second current mirror amplifier having respective input and output electrodes, the output electrode thereof being connected to said output terminal;
- means for connecting the output electrode of said first current mirror amplifier to the input electrode of said second current mirror amplifier;
- one of said first and second current mirror amplifiers comprising first and second transistors of like conductivity type having respective emitter, base and collector electrodes, means for connecting said collector electrode of said first transistor to said input electrode of said first current mirror amplifier;
- and means for connecting said first and second transistors as a current mirror amplifier wherein the current gain thereof decreases as the respective beta of said first and second transistors decrease;
- and
- the other of said first and second current mirror amplifiers comprising third and fourth transistors of like conductivity type having respective emitter, base, and collector electrodes, means for connecting said collector electrode of said third transistor to said input electrode of said second current mirror amplifier;
- and means for connecting said third and fourth transistors as a current mirror amplifier wherein the current gain thereof increases as the respective beta of said third and fourth transistors decreases.
5 more elements
An apparatus comprising:
- a first current mirror amplifier including a first input transistor and a first output transistor each having a conduction path and a control electrode for controlling the conduction of said conduction path, first means for connecting said first input transistor and said first output transistor as said first current mirror amplifier so that said conduction path of said first input transistor conducts substantially all of a first input current and said conduction path of said first output transistor conducts a first output current, said first means supplying control currents to said control electrodes of said first input transistor and said first output transistor derived substantially from said first input current;
- a second current mirror amplifier including a second input transistor and a second output transistor each having a conduction path and a control electrode for controlling the conduction of said conduction path, second means for connecting said second input transistor and said second output transistor as said second current mirror amplifier so that said conduction path of said second input transistor conducts substantially all of a second input current and said conduction path of said second output transistor conducts a second output current, said second means supplying control current to said control electrodes of said second input transistor and said second output transistor derived substantially from said second output current and being controlled in response to said second input current;
- means for applying a signal current to one of said first and second current mirror amplifiers as said respective input current;
- means for coupling the output current of said one current mirror amplifier to the other of said first and second current mirror amplifiers as said respective input current;
- and
- means for receiving said respective output current of said other current mirror amplifier and applying it to a load.
3 more elements
Dependencies are inferred from the claim text.