US 3,946,325 A · Transistor amplifier

Abstract

A differential amplifier stage, suitable for use as the first stage in an operational amplifier with a single power supply, has the capability of its input terminals being operated over a range including one of the supply potentials. The differential amplifier stage includes a pair of emitter-coupled transistors of a first conductivity type having their base electrodes connected to input signal terminals. These transistors are each provided with an active collector load by grounded-emitter transistors of the second conductivity type connected collector-to-collector therewith. Commonmode feedback from these collector-to-collector connections to the base electrode of the grounded-emitter transistors is used to regulate the emitter-to-collector potentials of these grounded-emitter transistors to a lower value than their emitter-to-base potentials, but to a value larger enough to avoid saturation.

Claims13

Dependent claims

The combination of:

first and second transistors of opposite conductivity types, each of said first and said second transistors having base and emitter electrodes with a base-emitter junction therebetween and having a collector electrode connected to that of the other at an interconnection;
means for applying a reference potential to the emitter electrode of said first transistor;
means for applying a forward bias potential between the emitter and base electrodes of said first transistor;
means for maintaining a potential between the emitter and collector electrodes of said first transistor which has a quiescent value substantially one-half as large as that of said forward bias potential;
and
further means connecting said second transistor as an amplifier with collector loading, said further means including means for applying an input signal between the base and emitter electrodes of said second transistor, said input signal having a direct component associated therewith related to said reference potential.

3 more elements

A differential amplifier comprising:

first and second transistors of a first conductivity type, each having a base and an emitter and a collector electrode;
means for applying a quiescent bias potential at a reference potential level to the base electrodes of each of said first and said second transistors;
means for coupling the emitter electrodes of said first and said second transistors together;
means for supplying a quiescent emitter current to each of said first and said second transistors, thereby to develop a quiescent emitter potential for each of said first and said second transistors;
and
means for maintaining the quiescent collector potentials of each of said first and said second transistors substantially midway between its emitter potential and said reference potential level.

3 more elements

A differential amplifier stage having:

first and second terminals for connection to a power supply;
third and fourth terminals for receiving an input signal;
first and second transistors of a first conductivity type, having respective emitter electrodes connected to a first node, having respective base electrodes respectively connected to said third terminal and to said fourth terminal, having respective collector electrodes respectively connected to a second node and to a third node;
direct current conductive means connecting said first terminal to said first node;
third and fourth transistors of a second conductivity type complementary to said first conductivity type, having respective base electrodes connected to a fourth node, having respective emitter electrodes directly connected to said second terminal, and having respective collector electrodes respectively connected to said second node and to said third node;
and
means providing common-mode feedback connecting each of said second and said third nodes to said fourth node including:
first means for translating potential, connected between said second node and a fifth node and poled for making the potential between said second terminal and said fifth node larger than the potential between said second terminal and said second node;
second means for translating potential connected between said third node and a sixth node and poled for making the potential between said second terminal and said sixth node larger than the potential between said second terminal and said third node;
third means for translating potential, providing potential translation smaller than that of said first means for translating potential by an amount .DELTA.V larger than the collector-to-emitter saturation potentials of said third and said fourth transistors, connected between said fifth and said fourth nodes and poled for making potential between said second terminal and said fourth node smaller than the potential between said second terminal and said fifth node;
and
fourth means for translating potential, providing potential translation smaller than that of said second means for translating potential by an amount .DELTA.V, connected between said sixth and said fourth nodes and poled for making the potential between said second terminal and said fourth node smaller than the potential between said second terminal and said sixth node, .DELTA.V being chosen to have a value substantially one-half that of the offset potentials applied between the base and emitter electrodes of each of said third and said fourth transistors by said common-mode feedback.

9 more elements

A differential amplifier stage having:

first and second terminals for connection to a power supply;
third and fourth terminals for receiving an input signal;
first and second transistors of a first conductivity type, having respective emitter electrodes connected to a first node, having respective base electrodes respectively connected to said third terminal and to said fourth terminal, having respective collector electrodes respectively connected to a second node and to a third node;
first direct current conductive means connecting said first terminal to said first node;
third and fourth transistors of a second conductivity type complementary to said first conductivity type, having respective base electrodes connected to a fourth node, having respective emitter electrodes directly connected to said second terminal, and having respective collector electrodes respectively connected to said second node and to said third node;
and
means providing common-mode feedback connecting each of said second and said third nodes to said fourth node including:
fifth and sixth transistors of said first conductivity type and a seventh transistor of said second conductivity type, each of these transistors having base and emitter electrodes with a base-emitter junction therebetween and having a collector electrode, the base electrodes of said fifth and said sixth transistors respectively connected to said second and said third nodes, the collector electrodes of said fifth and sixth transistors being connected to said second terminal, the emitter electrode of said seventh transistor being connected to said fourth node and the collector electrode of said seventh transistor being connected to said first terminal;
first and second resistive means having substantially equal resistances, said first resistance means being connected between said fifth transistor emitter electrode and said seventh transistor base electrode, said second resistive means being connected between said sixth transistor emitter electrode and said seventh transistor base electrode;
and
means for supplying current to the interconnection of said seventh transistor base electrode and said first and said second resistive means, poled to forward bias the base-emitter junctions of said fifth and said sixth and said seventh transistors.

8 more elements

Dependencies are inferred from the claim text.

Transistor amplifier

Life of this patent

Transistor amplifier

Life of this patent

Abstract

Claims13