Differential Audio Amplifier
AssigneeRed Lion 49 Limited
InventorDavid Joseph Mate
Life of this patent
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Abstract
A differential audio amplification apparatus with common mode rejection is shown, having a first input current path (401) and a second input current path (402) with a shunting input resistance (400) therebetween. The apparatus also has a first output current path (403) and a second output current path (404) with a shunting output resistance (405) therebetween. Differential amplifiers (412, 413) are provided with feedback connecting the input paths with the output paths and providing an output signal. The output shunting resistance (405) is controlled to provide gain control while maintaining common mode rejection.
Claims20
Differential audio amplification apparatus with common mode rejection, comprising:
- a first input current path and a second input current path with a shunting input resistance therebetween;
- a first output current path and a second output current path with a shunting output resistance therebetween;
- differential amplifiers with feedback connecting the input paths with the output paths and providing an output signal;
- wherein
- said output shunting resistance includes a controllable resistance circuit and is controlled to provide gain control while maintaining common mode rejection.
A method of amplifying a differential input signal having a first part and a complementary second part, comprising the steps of:
- applying a first part of a differential signal to a first input current path;
- applying a second part of a differential signal to a second input current path, in which said second current path is connected to said first current path via a shunting input resistance;
- supplying signals from said first and second input current paths via differential amplifiers to first and second output current paths;
- and
- controlling the resistance of an output shunting resistance connected between the first output current path and the second output current path to provide input gain control while maintaining common mode rejection.
A method of providing input stage amplification for a differential input signal produced by a microphone, comprising the steps of:
- applying a first part of a differential input signal to a first input current path;
- applying a second part of a differential input signal to a second input current path;
- supplying signals from said input current paths to a first output current path via a first operational amplifier;
- supplying signals from said input current paths to a second output current path via a second operational amplifier;
- connecting said first input current path to said first output current path via a first current mirror;
- connecting said second input current path to said second output current path via a second current mirror;
- and
- controlling the resistance of an output shunting resistance connected between the first output current path and the second output current path to provide input stage gain control while maintaining common mode rejection.
Dependencies are inferred from the claim text.