# US 2019/0245494 A1 · Power amplifier

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- Number: US 2019/0245494 A1
- Document ID: US20190245494A1
- Status: Published application
- Kind: A1
- Application number: 16/383,818
- Filed: 2019-04-15
- Published: 2019-08-08
- Earliest claimed: 2016-10-21
- Assignees: Yamaha Corporation
- Applicants: Yamaha Corporation
- Inventors: Yohei OHTANI
- Web page: https://patentgrep.com/patent/US20190245494A1

## CPC

- H03F 1/34: Negative-feedback-circuit arrangements with or without positive feedback (H03F1/02 - H03F1/30, H03F1/38 - H03F1/50, H03F3/50 take precedence {; for rejection of common mode signals H03F3/45479})
- H03F 3/187: in integrated circuits
- H03F 3/211: {using a combination of several amplifiers (H03F3/60 takes precedence)}
- H03F 3/217: Class D power amplifiers; Switching amplifiers
- H03F 3/2171: {with field-effect devices (H03F3/2173 - H03F3/2178 take precedence)}
- H03F 3/2178: {using more than one switch or switching amplifier in parallel or in series (H03F3/2173, H03F3/2175 take precedence)}
- H03F 3/45475: {using IC blocks as the active amplifying circuit}
- H03F 2200/03: the amplifier being designed for audio applications
- H03F 2200/129: there being a feedback over the complete amplifier
- H03F 2200/144: the feedback circuit of the amplifier stage comprising a passive resistor and passive capacitor
- H03F 2200/171: A filter circuit coupled to the output of an amplifier
- H03F 2200/267: A capacitor based passive circuit, e.g. filter, being used in an amplifying circuit
- H03F 2200/351: Pulse width modulation being used in an amplifying circuit
- H03F 2200/537: A transformer being used as coupling element between two amplifying stages
- H03F 2203/21157: A filter circuit being added at the output of a power amplifier stage
- H03F: AMPLIFIERS

## Abstract

A power amplifier includes a signal input unit to which an input signal is applied, an output stage that is electrically isolated from the signal input unit, where the output stage is configured to amplify an output signal of the signal input unit based on a power supply voltage from a floating power supply, a reference potential switch that is inserted between a reference node of the power supply voltage generated by the floating power supply and a reference potential line, and a feedback circuit configured to amplify a differential voltage between an output node of the output stage and the reference node, and feed the resultant voltage back to the signal input unit.

## Claims

### Claim 1

A power amplifier comprising:
a signal input unit to which an input signal is applied;
an output stage that is electrically isolated from the signal input unit, where the output stage is configured to amplify an output signal of the signal input unit based on a power supply voltage from a floating power supply;
a reference potential switch that is inserted between a reference node of the power supply voltage generated by the floating power supply and a reference potential line; and
a feedback circuit configured to amplify a differential voltage between the reference node and an object driven by an output of the output stage, and feed the amplified differential voltage back to the signal input unit.

### Claim 2 (depends on 1)

The power amplifier according to claim 1, wherein the feedback circuit includes:
a first inverting amplifier configured to invert and amplify a voltage for the object driven by the output of the output stage;
a second inverting amplifier configured to invert and amplify a voltage of the reference node of the floating power supply; and
a differential amplifier configured to invert and amplify a difference between an output signal of the first inverting amplifier and an output signal of the second inverting amplifier.

### Claim 3 (depends on 1)

The power amplifier according to claim 1, further comprising a filter configured to pass components in a specific band included in a differential voltage between an output node of the output stage and the reference node of the floating power supply, and
wherein the feedback circuit is configured to amplify components in an audio band included in the differential voltage between the output node and the reference node and a differential voltage between an output node of the filter and the reference node, and feeds the amplified differential voltage back to the signal input unit.

### Claim 4

A power amplifier comprising: two or more power amplification units, wherein each of the two or more power amplification units includes:
a signal input unit to which an input signal is applied;
an output stage that is electrically isolated from the signal input unit, where the output stage is configured to amplify an output signal of the signal input unit based on a power supply voltage from a floating power supply;
a reference potential switch that is inserted between a reference node of the power supply voltage generated by the floating power supply and a reference potential line; and
a feedback circuit configured to amplify a differential voltage between the reference node and an object driven by an output of the output stage, and feed the amplified differential voltage back to the signal input unit.