MOSFET Difference Amplifier With Programmable Feedback Taps
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Solution Overview
Problem
Existing amplifier circuits face challenges in accurately measuring small electrical signals from sensors like PIR and thermopile sensors due to high output impedance, charge build-up, and noisy environments, requiring sensitive instruments and specific operational modes to maintain signal fidelity and accuracy.
Innovation Solution
The proposed amplifier circuit uses a differential difference configuration with MOSFETs, incorporating a resistor divider with programmable voltage taps and additional capacitance to enhance integrator action, allowing direct feedback application to transistors for improved noise performance and flexibility in handling differential and single-ended signals, suitable for sigma-delta converters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a differential amplifier stage with high resistor values is used to reduce power consumption, then power consumption is reduced, but noise performance deteriorates due to the resistor connected between the sources of the two transistors
Solution Approach 1:
The patent extracts the harmful resistor element from the circuit topology. Instead of using a resistor connected between the sources of the two transistors (which generates noise), the invention uses a current source connected to a common reference potential. This removes the noise-generating component while maintaining the differential amplifier's power consumption benefits.
Solution Approach 2:
The patent changes the key parameter of the biasing mechanism from a resistive connection to a current source connection. By changing from a resistor-based bias network to a current source with high output impedance, the circuit achieves low power consumption while avoiding the thermal noise that plagues resistor-based designs.
2Adaptability or versatility
If early analogue-to-digital conversion is implemented to improve signal processing flexibility and reduce environmental interference, then signal processing flexibility is improved, but the complexity of the measurement device increases
Solution Approach 1:
The patent merges the amplifier and ADC functions into a tightly integrated system. The differential amplifier directly interfaces with the sigma-delta modulator, creating a unified signal path that reduces the number of separate components and interconnections, thereby managing complexity while maintaining processing flexibility.
Solution Approach 2:
The patent implements feedback mechanisms within the amplifier-ADC system to improve signal accuracy. The sigma-delta architecture uses quantization error feedback to achieve high-resolution conversion, allowing flexible signal processing without requiring overly complex external circuitry.
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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 (ch, cfe), 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 (v 1 , v 2 ), 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 (d 1 , d 2 ). 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 (d 1 , d 2 ) of the resistor divider (RREF) determined by the feedback signal ( S FB ).