| US 7,463,089 B1 | ||
| Class D audio power amplifier for mobile applications | ||
| Sumant Bapat, Santa Clara, Calif. (US); Ansuya Bhatt, Cupertino, Calif. (US); Christopher B. Heithoff, Sunnyvale, Calif. (US); and Raminder Jit Singh, San Jose, Calif. (US) | ||
| Assigned to National Semiconductor Corporation, Santa Clara, Calif. (US) | ||
| Filed on Jul. 28, 2006, as Appl. No. 11/460,937. | ||
| Int. Cl. H03F 3/88 (2006.01) | ||
| U.S. Cl. 330—10 [330/207 A] | 20 Claims |
| 1. A class D amplifier, comprising:
a supply-independent reference voltage generation circuit having at least an output;
a fully differential amplifier having at least a first input, a second input, a common mode voltage input, a first output,
and a second output, wherein the common mode voltage input is coupled to the output of the supply-independent reference voltage
generation circuit;
an integrator having at least a first input, a second input, a first output, and a second output, wherein the first input
of the integrator is coupled to the first output of the fully differential amplifier, the second input of the integrator is
coupled to the second output of the fully differential amplifier, and wherein the integrator includes a first op amp having
at least a first input and a second input;
a modulation circuit having a first input and a second input, wherein the first input of the pulse modulation circuit is coupled
to the first output of the integrator, and wherein the second input of the pulse modulation circuit is coupled to the second
output of the integrator; and
an active feedback circuit having at least a first input, a second input, a first output, and a second output, wherein the
first input of the active feedback circuit is coupled to a first class D amplifier output node, the second input of the active
feedback circuit is coupled to a second class D amplifier output node, the first output of the active feedback circuit is
coupled to the first input of the first op amp, and the second output of the active feedback circuit is coupled to the second
input of the first op amp.
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