PGA Resistor Network Layout for Low-Noise Wide Gain Range
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Solution Overview
Problem
Existing programmable gain amplifier (PGA) designs require large areas and offer poor performance to achieve a wide range of selectable gain, with high power consumption and thermal noise due to the need for large equivalent resistance in the resistor network.
Innovation Solution
A resistor network is introduced in the feedback loop with a configuration that uses less equivalent resistance, reducing the number of critical matching devices and improving CMRR and PGA gain error performance, while also being implemented on a smaller die area and lowering power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If traditional resistor networks are used in PGA feedback loops, then gain range can be achieved, but equivalent resistance is large causing high power consumption and thermal noise
Solution Approach 1:
The patent changes the resistance parameter by using parallel resistor configurations instead of series configurations. This transforms the equivalent resistance from a large value to a smaller value, directly reducing power consumption and thermal noise while maintaining the same gain range capability through reconfigured resistor networks.
Solution Approach 2:
The patent segments the feedback resistor into multiple parallel resistors rather than using a single large resistor or series combination. This segmentation allows the equivalent resistance to be reduced while still achieving the required gain range, thereby lowering power consumption and thermal noise generation.
2Area of stationary object
If traditional resistor networks are used in PGA feedback loops, then gain range can be achieved, but die area is large
Solution Approach 1:
The patent changes the resistance network configuration from series to parallel arrangements, which reduces the total equivalent resistance and consequently reduces the physical space required for the resistor network on the die, while improving matching performance through the parallel configuration.
Solution Approach 2:
The patent reconfigures the resistor network in a different dimensional arrangement by using parallel connections instead of series connections. This dimensional change in the circuit topology reduces the linear space required for the resistor network while maintaining or improving the matching characteristics.
3Measurement precision
If traditional resistor networks are used in PGA feedback loops, then gain range can be achieved, but CMRR and gain error performance are poor
Solution Approach 1:
The patent changes the resistor network configuration to parallel arrangements, which reduces the equivalent resistance and improves the matching characteristics. This parameter change leads to better CMRR and gain error performance while reducing the number of critical matching devices required.
Data Source
AI summary
A circuit includes an operational amplifier and a resistor network coupled to an output of the operational amplifier. The resistor network includes a first set of resistors coupled between the output of the operational amplifier and a first node of the resistor network, wherein the resistors of the first set are electrically connected in series with each other, a second set of resistors coupled between the first node and a second node of the resistor network, wherein the resistors of the second set are electrically connected in series with each other and include a first number of resistors, a third set of resistors coupled between the second node and a third node of the resistor network, wherein the third node is coupled to a first voltage, and wherein the resistors of the third set are electrically connected in parallel with each other and include a second number of resistors, and a resistor coupled between the first node and the second node and arranged in parallel with the second set of resistors.