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US 7,880,548 B2Granted
Headphone amplifier circuit
AssigneeAnalog Devices, Inc.
InventorsJinghua Ye, Hui Shen, Danny Li
Life of this patent
Estimating the term…
Abstract
A class G headphone amplifier circuit with improved power efficiency and low EMI. It may use an automatic signal level detector to detect the signal level of incoming signals and determine positive and negative power supplies for headphone amplifiers accordingly. A voltage generator may generate pairs of differential output voltages at a plurality of amplitude steps, and supply to headphone amplifiers the pair with the amplitude determined by the automatic signal level detector. As a result, headphone amplifiers are biased according to the input signal level, and the multiple voltage rails may improve power efficiency and avoid clipping.
Claims18
An amplifier circuit, comprising:
- a signal level detector, comparing an incoming signal with a first threshold and providing a first control signal when the incoming signal exceeds the first threshold and a second control signal when the incoming signal does not exceed the first threshold;
- a voltage generator, coupled to the signal level detector and generating a positive output voltage at a first amplitude when receiving the first control signal and a positive output voltage at a second amplitude when receiving the second control signal;
- and
- an amplifier, receiving at a positive power supply terminal the positive output voltage from the voltage generator,
- wherein the voltage generator further generates a negative output voltage at the first amplitude when receiving the first control signal and a negative output voltage at the second amplitude when receiving the second control signal;
- and wherein the amplifier receives at a negative power supply terminal the negative output voltage from the voltage generator.
3 more elements
An amplifier circuit, comprising:
- a signal level detector, comparing an incoming signal with a first threshold and providing a first control signal when the incoming signal exceeds the first threshold and a second control signal when the incoming signal does not exceed the first threshold;
- a voltage generator, coupled to the signal level detector and generating a positive output voltage at a first amplitude when receiving the first control signal and a positive output voltage at a second amplitude when receiving the second control signal;
- an amplifier, receiving at a positive power supply terminal the positive output voltage from the voltage generator;
- and
- a response speed controller for the signal level detector which compares the incoming signal with a predetermined value, and selects a fast response speed when the incoming signal exceeds the predetermined value.
2 more elements
A method for powering a headphone amplifier, comprising:
- comparing an incoming signal with a first threshold and providing a first control signal when the incoming signal exceeds the first threshold and a second control signal when the incoming signal does not exceed the first threshold;
- generating a positive output voltage at a first amplitude in response to the first control signal and a positive output voltage at a second amplitude in response to the second control signal;
- powering an amplifier with the positive output voltage;
- and
- generating a negative output voltage at the first amplitude in response to the first control signal and a negative output voltage at the second amplitude in response to the second control signal;
- and powering the amplifier with the negative output voltage.
3 more elements
A method for powering a headphone amplifier, comprising:
- comparing an incoming signal with a first threshold and providing a first control signal when the incoming signal exceeds the first threshold and a second control signal when the incoming signal does not exceed the first threshold;
- generating a positive output voltage at a first amplitude in response to the first control signal and a positive output voltage at a second amplitude in response to the second control signal;
- powering an amplifier with the positive output voltage;
- comparing the incoming signal with a second threshold and providing a third control signal when the incoming signal exceeds the second threshold and a fourth control signal when the incoming signal does not exceed the second threshold;
- and
- generating a positive output voltage at a third amplitude in response to the third control signal and a positive output voltage at a fourth amplitude in response to the fourth control signal.
3 more elements
A method for powering a headphone amplifier, comprising:
- comparing an incoming signal with a first threshold and providing a first control signal when the incoming signal exceeds the first threshold and a second control signal when the incoming signal does not exceed the first threshold;
- generating a positive output voltage at a first amplitude in response to the first control signal and a positive output voltage at a second amplitude in response to the second control signal;
- powering an amplifier with the positive output voltage;
- comparing the incoming signal with a predetermined value, and setting the signal level detector to work at a fast response speed when the incoming signal exceeds the predetermined value;
- and
- setting the signal level detector to work at a slower response speed when the incoming signal is lower than the predetermined value for a predetermined period of time.
3 more elements
An amplifier system, comprising:
- a signal level detector to compare an information signal with a predetermined threshold and to generate a control signal responsive thereto,
- a multi-mode charge pump having a pair of differential output terminals to generate pairs of differential output voltages at a plurality of voltage levels, a mode of the charge pump controlled by the control signal, and
- an amplifier having power supply terminals coupled to the charge pump output terminal and having an input for the information signal.
Dependencies are inferred from the claim text.