Differential Peak Detector With Common-Mode Flicker Noise Cancellation
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Solution Overview
Problem
Existing peak detector circuits are compromised by DC noise, particularly flicker noise, which affects the accuracy of their output, and existing mitigation techniques either increase costs or reduce operational speed, or fail to adequately reduce noise levels.
Innovation Solution
A circuit design that includes a differential input, a common mode detection circuit, a primary signal circuit, a replica block, and a summer to offset correlated flicker noise, using a common mode voltage to reduce noise in the peak detector output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If higher area devices are used in the circuit block preceding the peak detector to reduce flicker noise, then noise reduction is improved, but device area increases and operational speed decreases
Solution Approach 1:
The circuit is divided into multiple functional blocks: a first differential circuit for peak detection, a common mode detection circuit for noise detection, and a summer for combining signals. This segmentation allows each block to be optimized independently, enabling noise reduction without sacrificing speed.
Solution Approach 2:
The common mode detection circuit extracts the flicker noise component from the differential input signal by detecting the common mode voltage. This extracted noise signal is then processed separately and subtracted from the peak detector output, removing the harmful noise without affecting the main signal path speed.
2Object-affected harmful factors
If higher area devices are used in the circuit block preceding the peak detector to reduce flicker noise, then noise reduction is improved, but manufacturing cost increases
Solution Approach 1:
The common mode detection circuit uses a replica of the first differential circuit's topology (with transistors M20-M23 mirroring M2-M5) to generate a noise signal that matches the actual noise characteristics. This copying approach allows accurate noise modeling using standard-sized devices rather than requiring larger, more expensive noise-reduction devices.
3Object-affected harmful factors
If common mode voltage injection is used to reduce flicker noise, then some noise reduction is achieved, but flicker noise effect is not reduced to a satisfactory level
Solution Approach 1:
The common mode detection circuit continuously monitors the common mode voltage at the differential input and uses this feedback to dynamically adjust the noise compensation signal. The summer combines the peak detector output with the inverted noise signal, creating a closed-loop system that actively cancels flicker noise throughout operation, achieving satisfactory noise reduction levels.
Solution Approach 2:
The output signal is formed by combining two distinct signal components: the peak detector DC output and the common mode noise signal (after inversion). This composite signal approach allows the beneficial peak detection function to coexist with active noise cancellation, achieving both accurate peak measurement and satisfactory flicker noise reduction simultaneously.
Data Source
AI summary
A circuit with a differential input configured to receive a differential analog input signal. The circuit also includes a common mode detection circuit, a primary signal circuit coupled, and a replica block. The circuit also includes a summer coupled to the output of the primary signal circuit and to an output of the replica block.