Amplifier circuit to enable accurate measurement of small electrical signals
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Solution Overview
Problem
Existing amplifier circuits struggle with accurately measuring small electrical signals from sensors due to high output impedance, charge build-up, noisy environments, and the need for low power consumption, while maintaining high signal-to-noise ratio and dynamic range, especially in applications like passive infrared detection.
Innovation Solution
An amplifier circuit with a resistor divider and differential pair of transistors, where the resistor divider has addressable switch elements controlled by a feedback signal to select voltage taps, and the transistors' bulk terminals affect their threshold, allowing for differential or single-ended signal processing with low noise and low power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a high-value resistor is used in the amplifier circuit to maintain low current consumption, then power consumption is reduced, but noise performance deteriorates due to increased thermal noise
Solution Approach 1:
The single high-value resistor is segmented into multiple resistive elements connected in series. This segmentation allows the circuit to achieve the equivalent high resistance value needed for low power consumption while distributing the noise contribution across multiple elements, thereby improving overall noise performance and signal-to-noise ratio.
Solution Approach 2:
The circuit dynamically selects between different resistance values using switch elements that can connect different portions of the resistive element string to the amplifier input. This dynamic resistance selection allows optimization of the signal-to-noise ratio for different input signal conditions while maintaining low power consumption through the high-resistance path.
2Measurement precision
If the amplifier circuit uses a complex resistor network to achieve precise voltage division and low noise, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The resistive element string with switch elements serves multiple functions simultaneously: it provides precise voltage division for the non-inverting input, acts as a noise-reducing impedance network, and enables dynamic resistance selection. This multi-functionality achieves high measurement precision without proportionally increasing circuit complexity.
Solution Approach 2:
The circuit changes the resistance parameter dynamically by selecting different portions of the resistive element string based on signal conditions. This parameter change capability allows the circuit to optimize its performance characteristics, achieving precise voltage division and low noise without requiring multiple fixed resistor networks.
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
Enables accurate measurement of small electrical signals with low noise, high signal-to-noise ratio, and wide dynamic range, suitable for battery-operated devices, and is applicable in sigma-delta converters.
Implementation Method 1
a resistor divider (RREF) comprising n resistive elements (rn) in series where n>1, wherein: the resistor divider (RREF) comprises two main nodes defined at each end thereof, namely a first main node (a) and a second main node (b)
Implementation Method 2
a differential pair of transistors (T1, T2) comprising a first transistor (T1) having at least four terminals and a second transistor (T2) having at least four terminals, wherein: first terminals of each of the transistors (T1, T2) are connected to the second node (b)
Implementation Method 3
fourth terminals of the transistors (T1, T2) are connected to the respective readout nodes (d1, d2); wherein the amplifier circuit is configured to perform a function of a difference amplifier in that the transistors (T1, T2) form a differential amplifier with respective input signals (v1, v2) on their second terminals
Data Source
AI summary
An amplifier circuit includes a resistor divider (RREF) comprising n resistive elements, two main nodes defined at each end thereof, two readout nodes (d1, d2), resistor nodes (q) defined between adjacent resistive elements, and an input current source (IREF) connected or connectable to the first main node (a). The resistor divider (RREF) comprises two arrays of addressable switch elements controllable by a feedback signal (sFB) to be open or closed. The amplifier circuit includes a differential pair of transistors (T1, T2), wherein source terminals of each of the transistors (T1, T2) are connected to the second node (b), gate terminals of the transistors (T1, T2) are connected to input signals (v1, v2), drain terminals of the transistors (T1, T2) are connected to current sources (I1, I2), and bulk terminals of the transistors (T1, T2) are connected to the readout nodes (d1, d2). The amplifier circuit functions as a difference amplifier, wherein the bulk terminals affect a threshold of the respective transistors (T1, T2) so as to add or subtract a differential signal derived from the readout nodes (d1, d2) of the resistor divider (RREF) determined by the feedback signal (sFB).