Audio power amplifier with automatic bias control
AssigneeNorlin Music, Inc.
InventorsGene S. Morez, James F. Griffin
Life of this patent
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Abstract
A power amplifier with an automatic bias control circuit is disclosed. The amplifier includes two complementary Darlington pairs operating in a push-pull mode providing output power. A bias control network including a switching transistor is coupled to the base circuits of the Darlington pairs for controlling the bias current delivered to the pairs. The transistor is switched on and off by a detecting circuit which senses the presence of input signals applied to the amplifier. The bias control network operates to minimize power consumption by the Darlington pairs when no input signal is present and to raise the bias level of the Darlington pairs without distortion in the output signal when an input is applied to the amplifier.
Claims10
A power amplifier circuit including an automatic bias control comprising:
- power amplifier means including an input terminal for amplifying signals applied to said input terminal;
- and
- automatic bias control means coupled to said power amplifier for changing the state of said power amplifier from class B to class AB operation in response to an increasing signal level at said input terminal wherein said automatic bias control means includes
- a high gain amplifier,
- means for applying a signal which is a function of an input signal to said high gain amplifier,
- detector means coupled to said high gain amplifier for converting the output signal thereof to a bias control signal;
- and
- electronic switching means coupled to said detector circuit means for switching between conductive and non-conductive states in response to said bias control signal.
A power amplifier circuit including an automatic bias control comprising:
- power amplifier means including an input terminal for amplifying signals applied to said input terminal;
- and
- automatic bias control means coupled to said power amplifier for changing the state of said power amplifier from class B to class AB operation in response to an increasing signal level at said input terminal wherein said automatic bias control means includes
- a high gain amplifier, and
- means for applying a signal which is a function of an input signal to said high gain amplifier, the output from said high gain amplifier being a bias control signal.
A push-pull power amplifier including a circuit for automatically controlling the biasing of the output stages of said power amplifier, comprising:
- first means coupled to said output stages for normally providing a selected bias resistance between said stages, said first means including a predetermined resistance, and switching means for partially shunting said resistance;
- second means coupled to said amplifier for applying an input signal to said amplifier;
- and,
- third means coupled to said first means for significantly increasing the bias resistance between said output stages in response to an input signal being applied to said amplifier, said third means including means for opening said switching means whereby said resistance is no longer shunted.
Dependencies are inferred from the claim text.