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US 4,360,785 AGranted
Transistor amplifiers exhibiting low input offset potentials
AssigneeRCA Corporation
InventorOtto H. Schade, Jr.
Life of this patent
Estimating the term…
Abstract
The input offset potential of a transistor amplifier exhibited by a grounded-emitter bipolar transistor or a grounded source enhancement-mode field effect transistor can be too large for certain applications. A preceding differential-input amplifier overcomes this problem.
Claims10
A current amplifier comprising:
- first and second transistors of a first conductivity type, each having respective common and output electrodes defining the ends of its principal current conduction path and having a respective input electrode, wherein the potential between its common and input electrodes controls the conduction through its principal current conduction path,
- an input terminal to which the output electrode of said first transistor connects;
- an output terminal to which the output electrode of said second transistor connects;
- a common terminal to which the common electrodes of said first and second transistors connect;
- and
- means connecting the output electrode of said first transistor to the input electrodes of said first and second transistors for completing a direct-coupled degenerative feedback loop that adjusts the input electrode potentials of said first and second transistors respective to their common electrode potentials to condition said first transistor to conduct via its principal current conduction path at least a portion of any current applied between said common and input terminals, being improved in that the potential between the common and output electrodes of said first transistor is maintained smaller than the potential between the common and input electrodes of said first transistor, and to that end including
- a differential-input amplifier having an inverting input connection, having a non-inverting input connection connected to said input terminal, and having an output connection connected to the input electrodes of said first and second transistors, and including
- means for applying a biasing potential between the inverting input connection of said differential-input amplifier and said common terminal, said biasing potential having a magnitude no greater than the potential between the input and common electrodes of said first and second transistors.
5 more elements
In combination with a differential-output amplifier supply first and second output currents each including at least a balanced signal component, and a source of current equal to the sum of the first and second output currents of said differential-output amplifier,
- a balanced-to-single-ended signal converter for developing a single-ended signal in response to said balanced signal components comprising:
- input and output terminals to which the first and second output currents of said differential-output amplifier are respectively applied, said single-ended signal being developed at said output terminal;
- a common terminal for receiving a reference potential;
- first, second, third and fourth bipolar transistors of like conductivity type having respective emitter electrodes connected to said common terminal and having respective collector and base electrodes, the collector electrodes of said first and second transistors respectively connected to said input terminal and to said output terminal;
- fifth and sixth, field-effect transistors of a conductivity type complementary to that of said bipolar transistors, having respective drain and gate electrodes and having respective source electrodes interconnected to receive said current equal to the sum of the first and second output currents of said differential-output amplifier;
- means for applying the potential at said input terminal to the gate electrode of said fifth transistor;
- means for applying a potential between the gate electrode of said sixth transistor and said common terminal;
- an interconnection between the collector electrode of said third transistor and the drain electrode of said fifth transistor, which interconnection connects to the base electrodes of said third and fourth transistors;
- and
- an interconnection between the collector electrode of said fourth transistor and the drain electrode of said sixth transistor, which interconnection connects to the base electrodes of said first and second transistors.
7 more elements
Dependencies are inferred from the claim text.