Programmable Gain Amplifier Resistor Ladder for Low Gain Error
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current programmable gain amplifier designs suffer from nonlinear errors due to the use of switches, which introduce impedance variations based on process, temperature, and voltage, leading to undesirable gain errors greater than 1% and occupying excessive semiconductor die area.
Innovation Solution
Implementing parallel current paths through resistor ladders using switches to bypass resistors, allowing control of resistance values RA and RB independently, thereby maintaining a feedback pole larger than the bandwidth and reducing nonlinearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If switches are used to control gain settings in the resistor ladder, then gain programmability is achieved, but nonlinear errors increase due to impedance variations
Solution Approach 1:
The resistor ladder is divided into multiple segments with tap points at different positions. By selecting different tap points and configuring switch connections, the feedback network is segmented into different effective resistance combinations, enabling multiple gain settings while maintaining accuracy through careful segment design
Solution Approach 2:
The patent changes the resistance parameters by using parallel resistor paths that can be selectively activated. The effective resistance values are changed by switching between different parallel combinations (e.g., R1||R2, R3||R4) rather than using simple series/parallel switch configurations, which reduces nonlinear errors
2Adaptability or versatility
If traditional switch configurations are used for gain control, then gain settings are achieved, but gain errors exceed 1% due to nonlinear effects
Solution Approach 1:
The patent introduces intermediate resistor elements (R1, R2, R3, R4) as mediators between the switches and the feedback network. These intermediate resistors buffer the nonlinear effects of the switches, allowing gain control while keeping errors below 1% by distributing the switching stress across multiple resistive paths
Solution Approach 2:
The feedback network uses composite resistor configurations combining multiple resistors in parallel and series arrangements. This composite structure allows the system to achieve precise gain settings by combining the effects of multiple resistive elements, reducing the impact of individual component tolerances and nonlinearities
3Measurement precision
If more switches are added for precise gain control, then gain precision is improved, but semiconductor die area increases
Solution Approach 1:
The switches in the patent serve multiple functions: they control both the selection of tap points and the configuration of parallel resistor paths. Each switch is part of a multi-functional network that achieves precise gain control without requiring a separate switch for each gain setting, thereby reducing the total switch count and die area
Solution Approach 2:
The patent merges the functions of gain selection and feedback configuration into a unified resistor ladder structure. Multiple gain settings are achieved by combining different tap point selections with different parallel path configurations, allowing precise control with fewer switches than traditional approaches
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Achieves gain settings with less than 1% error and efficient use of semiconductor die area by adjusting resistance values to maintain precision and desired gain across various settings.
Implementation Method 1
control a first switch, of the plurality of switches, to complete a first current path from a first node in the set of resistors ladder to a tap point
Implementation Method 2
control a second switch, of the plurality of switches, to complete a second current path from a second node in the set of resistors to the tap point
Implementation Method 3
the tap point divides a first resistive portion (RA) of the set of resistors between the tap point and ground and a second resistive portion (RB) of the set of resistors between the tap point and the amplifier output
Data Source
AI summary
A programmable gain amplifier (PGA) architecture provides for robust operation over a bandwidth and for a multitude of gain settings. For instance, the PGA architecture may include multiple switches to implement different current paths by bypassing resistors in a resistor ladder. The different current paths may result in different gain settings. In some implementations, the switches may be used to hold a value of RA constant while a value of RB may be varied over the different gain settings, where gain may be inferred from the equation Vout=Vin*(1+RB/RA).