US 2016/0079943 A1Published application

Two Differential Amplifier Configuration

AssigneeESS Technology, Inc.

InventorA. Martin Mallinson

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Abstract

An apparatus is disclosed for providing a common mode voltage to the inputs of a first differential amplifier which outputs the difference between two signals. A second differential amplifier receives the output of the first differential amplifier, and the output of the second differential amplifier is fed back to the inputs of the first differential amplifier as a common mode voltage. Since both inputs of the first differential amplifier receive the fed hack common mode voltage, the first differential amplifier still outputs only the difference in the two signals, but the presence of the common mode voltage allows the first differential amplifier to operate with lower noise if the voltage levels of the inputs to the first differential amplifier vary. The second differential amplifier may be of significantly lower quality and cost than the first differential amplifier, without affecting the performance of the first differential amplifier.

Claims11

Dependent claims

A circuit comprising:

a first differential amplifier, comprising:
a first operational amplifier having an inverting input for receiving a first part of a differential signal and a non-inverting input for receiving a second part of the differential signal, and an output for outputting a single ended signal representing the difference between the two parts of the differential signal;
a first resistor coupled to the output of the first operational amplifier and the inverting input of the first operational amplifier so as to create a negative feedback loop around the first operational amplifier;
and
a second resistor coupled to the non-inverting input of the first operational amplifier and to a ground;
a second differential amplifier, comprising:
a second operational amplifier having an inverting input and a non-inverting input, the non-inverting input coupled to the ground;
a third resistor coupled to the output of the first operational amplifier and to the inverting input, of second operational amplifier;
and
a fourth resistor coupled to the output of the second operational amplifier and the inverting input of the second operational amplifier so as to create a negative feedback loop around the second operational amplifier;
a fifth resistor coupled to the output of the second operational amplifier and the inverting input of the first operational amplifier;
and
a sixth resistor coupled to the output of the second operational amplifier and the non-inverting input of the first operational amplifier.

10 more elements

Dependencies are inferred from the claim text.

Facts

Application: 14/569,079Filed 12 Dec 2014
Priority: 12 Sep 2014
Published: 17 Mar 2016
Term ends: Not estimatedThe source records don’t support an estimate.

Classification18 codes

H03F 3/45076
With semiconductor devices only: characterised by the way of implementation of the active amplifying circuit in the differential amplifier
H03F 1/0205
Modifications of amplifiers to raise the efficiency, e.g. gliding Class A stages, use of an auxiliary oscillation: in transistor amplifiers
H03F 1/34
Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements:…
H03F 3/45475
Characterised by the way of implementation of the active amplifying circuit in the differential amplifier: using IC blocks as the active…