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US 5,208,865 AGranted
Muting circuit using common mode rejection of differential amplifier
AssigneeFord Motor Company
InventorsJames W. Friske, Andrew C. Krochmal
Life of this patent
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Abstract
Differential signals are employed in a distributed audio system to improve noise immunity of the low level differential signals transmitted between a main unit and a power amplifier. The power amplifier may be in an auxiliary output unit which is locally muted by employing a field-effect transistor connected between the differential signals. When the field-effect transistor is turned on by a mute signal, the common mode rejection of the differential amplifier is employed to mute the amplifier output.
Claims11
An audio system for a vehicle comprising:
- a source of audio signals to be reproduced;
- an audio processor coupled to said source and providing a low level differential output signal across a pair of output terminals;
- main controller means coupled to said source and said audio processor for controlling audio parameters of said low level differential output signal;
- primary output means coupled to said output terminals for amplifying said low level differential output signal and for reproducing sound in said vehicle;
- and
- auxiliary output means coupled to said output terminals for reproducing sound audible in a portion of said vehicle, said auxiliary output means comprising:
- a fixed gain differential amplifier having a pair of differential inputs coupled to receive said low level differential output signal;
- muting means coupled to said pair of differential inputs for selectably connecting together said differential inputs in response to a mute signal;
- and
- auxiliary controller means coupled to said muting means for generating said mute signal for a predetermined time when said audio processor is first activated.
7 more elements
A mutable audio system comprising:
- audio processor means for receiving input audio signals and providing a low level differential output signal across a pair of output terminals;
- a fixed gain differential amplifier having a pair of differential inputs coupled to receive said low level differential output signal;
- a pair of resistors, each respective resistor connected between a respective output terminal of said audio processor and a respective differential input;
- a first field-effect transistor connected between said differential inputs and receiving a mute signal at the gate thereof;
- and
- controller means coupled to said field-effect transistor for generating said mute signal when said audio system is to be muted.
3 more elements
Dependencies are inferred from the claim text.