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DE-102023105212-B4 - Techniques for external control of an amplifier's gain

DE102023105212B4DE 102023105212 B4DE102023105212 B4DE 102023105212B4DE-102023105212-B4

Abstract

Amplifier circuit with programmable gain, featuring the following: at least one device pin (208A) designed to be coupled to an external gain adjustment resistor component (RG); a resistor component chain (202) comprising several resistor components (206A-206H); a comparator chain (204) with several comparator circuits (U1-U8), wherein the several comparator circuits (U1-U8) have the following: first inputs, which are coupled in such a way that they receive voltages generated by corresponding components of the multiple resistors; and second inputs that are coupled in such a way that they receive a voltage applied to at least one device pin (208A); a logic circuit (210) with multiple inputs coupled to corresponding outputs of the multiple comparator circuits (U1-U8); and an amplifier component that is adjustable by the logic circuit (210) based on outputs of the multiple comparator circuits (U1-U8), wherein the logic circuit (210) is configured to adjust the gain of the amplifier component based on a comparison between the voltages from the resistor component chain (202) and the voltage applied to the at least one device pin (208A).

Inventors

  • Gregory Lawrence DiSanto

Assignees

  • ANALOG DEVICES, INC.

Dates

Publication Date
20260513
Application Date
20230302
Priority Date
20220309

Claims (13)

  1. Amplifier circuit with programmable gain, comprising: at least one device pin (208A) designed to be coupled to an external gain-adjusting resistor component (RG); a resistor chain (202) comprising multiple resistor components (206A-206H); a comparator chain (204) comprising multiple comparator circuits (U1-U8), wherein the multiple comparator circuits (U1-U8) comprise: first inputs coupled to receive voltages generated by corresponding resistor components; and second inputs coupled to receive a voltage applied to the at least one device pin (208A); a logic circuit (210) comprising multiple inputs coupled to corresponding outputs of the multiple comparator circuits (U1-U8); and an amplifier component which is adjustable by the logic circuit (210) based on outputs of the multiple comparator circuits (U1-U8), whereby the logic circuit (210) is configured to adjust a gain of the amplifier component based on a comparison between the voltages from the resistor component chain (202) and the voltage applied to the at least one device pin (208A).
  2. Amplifier circuit with programmable gain according to Claim 1 , wherein the comparator chain (204) is configured to generate a thermometer code.
  3. Amplifier circuit with programmable gain according to Claim 2 , where the logic switch tung (210) is designed to convert the thermometer code into a binary code.
  4. Amplifier circuit with programmable gain according to one of the Claims 1 until 3 , wherein the logic circuit (210) includes a level conversion circuit (228) for adjusting a voltage level of an output of the logic circuit (210).
  5. Amplifier circuit with programmable gain according to one of the Claims 1 until 4 , wherein the amplifier component comprises a first and a second amplifier component (402, 404) arranged in an instrumentation amplifier configuration.
  6. Amplifier circuit with programmable gain according to one of the Claims 1 until 5 , where the amplifier component is an amplifier component that has a differential input for receiving a differential input signal.
  7. Amplifier circuit with programmable gain according to Claim 6 , wherein the amplifier component further comprises a differential output for generating a differential output signal.
  8. Amplifier circuit with programmable gain according to one of the Claims 1 until 7 , where the amplifier component is an amplifier component arranged in a negative feedback configuration.
  9. Amplifier circuit with programmable gain according to one of the Claims 1 until 8 , comprising: a first current source (302) coupled to a first end of the resistor component chain (202); and a second current source (304) coupled to the at least one device pin (208A), wherein the second inputs of the multiple comparator circuits (U1-U8) are coupled such that they receive the voltage applied to the at least one device pin (208A) generated by an external gain-adjusting resistor component (RG) and the second current source.
  10. A method for operating a programmable gain amplifier circuit, comprising: Generating several voltages across corresponding resistive components (206A-206H) of a resistive component chain (202); Comparing corresponding voltages across the multiple voltages with a reference voltage generated across an external gain-adjusting resistor component (RG) by comparators (U1-U8) of a comparator chain (204); Determining a code based on the comparison; Generating a control signal based on the code; and Controlling, based on the control signal, at least one switch (214) to connect another resistive component (216) to adjust the gain of an amplifier component of the programmable gain amplifier circuit.
  11. Procedure according to Claim 10 , where determining the code based on the comparison involves: determining a thermometer code.
  12. Procedure according to Claim 11 , which includes the following: converting the thermometer code into a binary code.
  13. Procedure according to one of the Claims 10 until 11 , which features the following: Adjusting a voltage level of an output of a logic circuit (210).

Description

AREA OF REVELATION This document concerns amplifier circuits in general, but not exclusively, and in particular amplifier circuits with programmable gain. BACKGROUND Amplifiers can amplify a signal property, such as current, voltage, power, another signal property, or a combination thereof, of an incoming signal, such as an electrical signal. One type of amplifier is a programmable gain amplifier. A programmable gain amplifier may have adjustable resistors in a feedback path (from an amplifier output to an amplifier input), an input path (from an input terminal to the amplifier input), or both, to achieve varying gain levels. Some conventional amplifiers use a single external resistor to adjust the gain. The resistance value of this external resistor is used in the gain equation, which defines the amplifier's gain. Tolerances and inaccuracies in the external resistor can directly affect the overall performance of the amplifier. US 2010 / 0 194 620 A1 This describes a parallel analog-to-digital converter (ADC) with a comparator chain, a reference voltage ladder, and an encoder for converting thermometer codes into binary codes. To improve conversion accuracy, a mechanism for detecting and correcting so-called "bubbles" (errors in the thermometer encoding) is employed, and the clock ratios for sampling and comparison operations can also be dynamically adjusted. The circuit is thus used exclusively for digitizing analog input signals while minimizing encoding errors. US 10 103 742 B1 This concerns a multi-stage hybrid analog-to-digital converter (ADC) that combines a successive approximation register (SAR) stage and a flash ADC stage in a pipeline architecture. The goal is to unite high resolution, high speed, and low power consumption in a single system. The first and last stages consist of SAR ADCs, which operate in an energy- and area-efficient manner, while the middle stage is a fast flash ADC that handles time-critical conversions. DE 10 2015 117 109 A1 This document describes a device and a method for digitally controlling the output amplitude of an analog sensor signal. The invention comprises an analog main signal path that amplifies and outputs a sensor signal, and a digital control circuit that generates a digital control signal to compensate for gain errors or ratiometric behavior. The gain is adjusted, among other things, by digitally controllable resistor elements within an amplifier. BRIEF SUMMARY OF THE INVENTION This disclosure describes, among other things, techniques for setting the gain of an amplifier circuit where the external resistance of the amplifier circuit is used to determine a selectable internal gain setting. This approach contrasts with other approaches where a resistance value of the external resistor is used in the actual gain equation that determines the gain of the amplifier circuit. Here, a voltage across the external resistor can be compared to an on-chip reference and then used to program the desired gain. These techniques can reduce or eliminate the need for an exact external resistor and can enable significant improvements in initial gain accuracy and gain drift for existing boards and/or systems with just a change to the bill of materials. In some aspects, this disclosure relates to an amplifier circuit according to the invention as claimed in claim 1. In some aspects, this disclosure further relates to a method according to the invention for operating an amplifier circuit with programmable gain according to claim 10. This overview is intended to provide a summary of the subject matter of the present patent application. It is not intended to provide an exclusive or exhaustive explanation of the invention. The detailed description is included to provide further information about the present patent application. BRIEF DESCRIPTION OF THE DRAWINGS In drawings that are not necessarily drawn to scale, the same numbers can describe similar components in different views. The same numbers with different letter suffixes can represent different instances of similar components. The drawings represent, in a general, exemplary, but not limiting, manner, various embodiments discussed in this document. 1 This is an example of an amplifier circuit. 2 is an example of an amplifier circuit with programmable gain that can implement various techniques of this revelation. 3 is another example of an amplifier circuit with programmable gain that can implement various techniques of this revelation. 4 is another example of an amplifier circuit with programmable gain that can implement various techniques of this revelation. 5 is another example of an amplifier circuit with programmable gain that can implement various techniques of this revelation. 6 is another example of an amplifier circuit with programmable gain that can implement various techniques of this revelation. 7 This is a flowchart of an example of a method for operating an amplifier circuit with programmable gain. DETAILED DESCRIPTION