US 4,638,260 AGranted

Audio amplifier

OwnerJames P. Hamleyinventor

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Abstract

The input stage to an audio amplifier comprises a complementary-symmetry, differential amplifier pair which drives an intermediate voltage gain stage comprised of a complementary-symmetry, cascode differential amplifier pair. The intermediate stage provides signal drive and bias to the output power amplifier stage, which is preferably a bridged configuration. Control circuitry produces a composite bias signal which is the summation of a static bias signal and a dynamic bias signal. The bias control signal is coupled to the bias control circuit through an optical coupler, and a dynamic class A bias is achieved. Negative feedback for the amplifier is provided by a differential amplifier which has its differential inputs connected to the load terminals, thereby placing any connecting cable between the amplifier and load within the corrective feedback path.

Claims34

Dependent claims

An audio amplifier comprising:

an input stage for receiving a signal to be amplified;
an intermediate stage for gain amplifying the signal from the input stage;
and,
an output stage, adapted to be coupled to a load, for power amplifying the signal from the intermediate stage,
wherein said input stage comprises a complementary-symmetry, differential amplifier pair, each differential amplifier having first and second output terminals, said signal to be amplifier being coupled to the first input terminal of each of said amplifiers;
wherein said intermediate stage comprises a complementary-symmetry, cascode differential amplifier pair, each intermediate stage amplifier pair having first and second input terminals coupled to the first and second output terminals of one of said input stage differential pairs, and each intermediate stage having first and second output terminals;
wherein said output stage comprises power amplifier means connected to at least one of said output terminals from each of said intermediate stage amplifiers for power amplifying the signal thereon;
and
a feedback circuit coupled from said output stage to the second input terminal of each of said input stage differential amplifiers for applying a feedback signal thereto.

6 more elements

Dependencies are inferred from the claim text.

Facts

Application: 06/652,722Filed 21 Sep 1984
Granted: 20 Jan 1987
Term ends: Not estimatedThe source records don’t support an estimate.

Classification5 codes

H03F 1/34
Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements:…
H03F 3/085
Controlled by light: using opto-couplers between stages
H03F 3/3077
With symmetrical driving of the end stage: using Darlington transistors
H03F 2203/30066
Indexing scheme relating to single-ended push-pull [SEPP]; Phase-splitters therefor: a optical element being used in the bias circuit of the…