Amplifier circuit
AssigneeInfineon Technologies AG
InventorDerek Bernardon
Life of this patent
Estimating the term…
Abstract
The invention is directed to an amplifier circuit based on the principle of a class D amplifier. To avoid unwanted convolution effects and to improve the power supply rejection ratio, provision is made for the amplitude of the ramp signal used for pulse width modulation to track proportionally the supply voltage for the amplifier circuit. For this purpose, the ramp signal generator has an amplitude control input suitably connected to supply and reference potentials. This ensures a constant duty ratio which is independent of the supply voltage. The present circuit may be used, for example, as a DC/DC converter or as an audio amplifier.
Claims20
An amplifier circuit, comprising:
- an input configured to receive a useful signal to be amplified;
- an output configured to tap off or output an amplified version of the useful signal;
- a differential amplifier comprising a first input connected to the input of the amplifier circuit, a second input coupled to the output of the amplifier circuit, and an output;
- a comparator comprising a first input connected to the output of the differential amplifier, and a second input configured to receive a periodic signal;
- an output stage comprising an input coupled to an output of the comparator, an output coupled to the amplifier output, and a supply connection for receiving a supply voltage;
- and
- a signal generator connected to the second input of the comparator and configured to provide the periodic signal at an amplitude which is proportional to the supply voltage at the output stage, the signal generator configured as a phase locked loop to regulate a frequency of the periodic signal based on a reference clock.
An amplifier circuit, comprising:
- means for comparing an input signal of the amplifier circuit to an output signal of the amplifier circuit, and generating an error signal associated therewith;
- means for comparing the error signal and a periodic signal and outputting a pulse width modulation control signal in response to the comparison;
- an output stage configured to receive the pulse width modulation control signal and generate the amplifier circuit output signal in response;
- and
- means for generating the periodic signal, where the periodic signal has an amplitude which is proportional to a supply voltage at the output stage, wherein the means for generating is configured as a phase locked loop to regulate a freguency of the periodic signal based on a reference clock.
An amplifier circuit, comprising:
- a first operational amplifier circuit having a non-inverting input and an inverting input, respectively, and having a differential input signal coupled thereto, the first operational amplifier circuit having a differential output comprising a non-inverting output and an inverting output coupled to the inverting input and the non-inverting input thereof, respectively, through capacitive elements, the first operational amplifier circuit also having a differential output signal of the amplifier circuit coupled to the non-inverting and inverting inputs thereof, wherein the first operational amplifier circuit is configured to output an error signal at the non-inverting output thereof based on a difference between the differential input signal and the differential output signal;
- a comparator circuit having a first input coupled to the non-inverting input of the first operational amplifier circuit and receiving the error signal thereat, and a second input configured to receive a periodic signal, wherein the comparator is configured to output a pulse width modulation control signal based on a comparison of the error signal and the periodic signal;
- and
- a signal generator circuit configured to generate the periodic signal at an amplitude which is proportional to a supply voltage at an output stage, the signal generator configured as a phase locked loop to regulate a frequency of the periodic signal based on a reference clock.
Dependencies are inferred from the claim text.