Granted Patent B2

US 8,861,749 · App. 13/114,655 · Granted Oct 14, 2014

Abstract

Claims (32)

1. An audio output channel, comprising:

an on-chip audio channel amplifier that amplifies an audio signal suitable for an audio output device;

a channel output IC pin operably coupled to an output of the on-chip audio channel amplifier;

a channel feedback IC pin operably coupled to an input of the on-chip audio channel amplifier to provide a feedback loop;

a jack return connection coupled to the channel feedback IC pin;

an inductor having a first end coupled to the jack return connection and having a second end coupled to the channel output IC pin; and

wherein the inductor is operative to pass audio frequencies of the amplified audio signal at the channel output IC pin to the jack return connection while suppressing electromagnetic interference frequencies at the channel output IC pin from the jack return connection, in which the electromagnetic interference frequencies are higher than the audio frequencies.

2. The audio output channel of claim 1 , further comprising:

a resistive element having a first end coupled to the channel feedback IC pin and a second end coupled to the jack return connection; and

a capacitive element having a first end coupled to the channel output IC pin and a second node coupled to the channel feedback IC pin.

3. The audio output channel of claim 1 , wherein the inductor comprises a ferrite-core inductor.

4. The audio output channel of claim 1 , further comprising an antenna operably coupled to the jack return connection.

5. The audio output channel of claim 4 , wherein the antenna is a headphone lead.

6. The audio output channel of claim 1 , further comprising:

an on-chip DC reference voltage node;

an on-chip left channel audio amplifier coupled to the DC reference voltage node;

an on-chip right channel audio amplifier coupled to the DC reference voltage node; and

wherein the on-chip audio channel amplifier comprises a central audio channel amplifier having a non-inverting input coupled to the DC reference voltage node and having an inverting input coupled to the channel feedback IC pin.

7. An audio system, comprising:

a DC reference voltage node;

a left channel audio amplifier coupled to said DC reference voltage node;

a right channel audio amplifier coupled to said DC reference voltage node;

a center channel audio amplifier having a non-inverting input coupled to said DC reference voltage node, having a negative input, and having an output;

a jack return connection coupled to said inverting input of said center channel audio amplifier;

an inductor having a first end coupled to said jack return connection and having a second end coupled to said output of said center channel audio amplifier; and

wherein said inductor is operative to pass audio frequencies at said output of said center channel audio amplifier to said jack return connection while suppressing electromagnetic interference frequencies at said output of said center channel audio amplifier from said jack return connection, in which said electromagnetic interference frequencies are greater than said audio frequencies.

8. The audio system of claim 7 , further comprising:

a resistive element having a first end coupled to said inverting input of said center channel audio amplifier and a second end coupled to said jack return connection; and

a capacitive element having a first end coupled to said output of said center channel audio amplifier and a second node coupled to said inverting input of said center channel audio amplifier.

9. The audio system of claim 7 , wherein said inductor comprises a ferrite-core inductor.

10. The audio system of claim 7 , further comprising an antenna operably coupled to said jack return connection.

11. The audio system of claim 10 , wherein said antenna comprises a headphone lead.

Assignments (21)