Class d transconductance amplifier

Patent metadata

Field	Value
Publication number	US-2020366252-A1
Application number	US-202016986195-A
Country	US
Kind code	A1
Filing date	Aug 5, 2020
Priority date	Feb 15, 2019
Publication date	Nov 19, 2020
Grant date	—

Abstract

An amplifier circuit includes: a Schmidt trigger having an input electrically coupled to an input of the amplifier circuit, a switching network electrically coupled to an output of the Schmidt trigger, an inductor electrically coupled to the switching network, a first resistor electrically coupled to the inductor, a capacitor electrically coupled to the first resistor, a first feedback circuit that provides a first feedback signal to the input of the Schmidt trigger based on a voltage at a first node electrically coupled to the first resistor and to the capacitor, a second resistor electrically coupled to the output of the amplifier circuit, a third resistor electrically coupled to the second resistor, and a second feedback circuit that provides a second feedback signal to the input of the Schmidt trigger based on a voltage at a second node electrically coupled to the second resistor and to the third resistor.

First claim

1 . An amplifier circuit comprising:
a Schmidt trigger having an input electrically coupled to an input of the amplifier circuit; a switching network electrically coupled to an output of the Schmidt trigger; an inductor electrically coupled to the switching network, wherein based on a state of the switching network, the switching network provides a positive supply voltage or a negative supply voltage to the inductor, and wherein the inductor provides a circuit path for current to flow to an output of the amplifier circuit; a first resistor electrically coupled to the inductor; a capacitor electrically coupled to the first resistor; a first feedback circuit that provides a first feedback signal to the input of the Schmidt trigger based on a voltage at a first node electrically coupled to the first resistor and to the capacitor; a second resistor electrically coupled to the output of the amplifier circuit; a third resistor electrically coupled to the second resistor; and a second feedback circuit that provides a second feedback signal to the input of the Schmidt trigger based on a voltage at a second node electrically coupled to the second resistor and to the third resistor, wherein the current at the output of the amplifier circuit is proportional to an input voltage applied to the input of the amplifier circuit.

2 . The amplifier circuit according to claim 1 , wherein the first feedback circuit includes a first operational amplifier electrically coupled in series with a fourth resistor, and the second feedback circuit includes a second operational amplifier electrically coupled in series with a fifth resistor.

3 . The amplifier circuit according to claim 1 , wherein the switching network includes:
a first transistor having a gate that is electrically coupled to the output of the Schmidt trigger, and a source that is electrically coupled to the positive supply voltage; and a second transistor having a gate that is electrically coupled to the output of the Schmidt trigger via an inverter, and a drain that is electrically coupled to a negative supply voltage.

4 . The amplifier circuit according to claim 3 , wherein the inductor is electrically coupled to a drain of the first transistor and to a source of the second transistor, such that the inductor receives either the positive supply voltage via the first transistor or the negative supply voltage via the second transistor depending on the alternating signals provided by the Schmidt trigger.

5 . The amplifier circuit according to claim 1 , wherein a first terminal of the first resistor is electrically coupled to the inductor, to the first switch, and to the second switch; a second terminal of the first resistor is electrically coupled to a first terminal of the capacitor and to the first node; and a second terminal of the capacitor is electrically coupled to ground.

6 . The amplifier circuit according to claim 1 , wherein the Schmidt trigger provides hysteresis to the amplifier circuit.

7 . The amplifier circuit according to claim 1 , further comprising filter circuitry coupled to the inductor that smooths fluctuations in the magnitude of the current flowing through the inductor to the output of the amplifier circuit.

8 . A method comprising:
electrically coupling an input voltage to an input terminal of a Schmidt trigger; generating a control signal at an output terminal of the Schmidt trigger based on a voltage at the input terminal of the Schmidt trigger and hysteresis of the Schmidt trigger; electrically coupling a first terminal of an inductor to a first switch and a second switch; controlling the first switch and the second switch based on the control signal from the Schmidt trigger; electrically coupling a second terminal of the inductor to a first terminal of a first resistor; generating a feedback signal based on a difference between a first voltage at the first terminal of the first resistor and a second voltage at a second terminal of the first resistor; electrically coupling the feedback signal to the first input terminal of the Schmidt trigger; and outputting a current having a magnitude that is proportional to a magnitude of the input voltage.

9 . The method according to claim 8 , further comprising:
smoothing fluctuations in the magnitude of a current flowing through the inductor.

10 . The method according to claim 8 wherein the first resistor operates to sense a current flowing through the inductor, and wherein generating the feedback signal includes electrically coupling the first terminal of the first resistor as first input to an instrumentation amplifier and electrically coupling the second terminal of the first resistor as second input to the instrumentation amplifier, the instrumentation amplifier operating as a differential amplifier that produces the feedback signal based on the difference in the voltage applied as the first and second inputs to the instrumentation amplifier.

Assignees

• Fluke Corp

Inventors

• Britz William J
• Richards Jake R

Classifications

• H02M1/0009

  Devices or circuits for detecting current in a converter · CPC title

• H03F2200/171

  A filter circuit coupled to the output of an amplifier · CPC title

• G01R35/007

  Standards or reference devices, e.g. voltage or resistance standards, "golden references" · CPC title

• H02M3/158

  including plural semiconductor devices as final control devices for a single load · CPC title

• H03F2200/129

  there being a feedback over the complete amplifier · CPC title