Programmable Chopper Amplifier Banks for Low Offset and Ripple
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Solution Overview
Problem
Conventional chopper amplifiers face challenges in reducing input offset voltage while minimizing output voltage ripple and maintaining low power consumption and design complexity, as existing techniques like auto-zeroing and chopping introduce noise and increase bandwidth at the cost of power consumption and complexity.
Innovation Solution
A chopper amplifier with a programmable memory and differential transistor banks, where a selection circuit configures transistors into groups to minimize input offset voltage by selecting optimal transistor configurations based on calibration data stored in memory, reducing output ripple and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional chopper circuitry is used to reduce input offset voltage, then input offset voltage is reduced, but output voltage ripple increases at chopping frequency and harmonics
Solution Approach 1:
The amplifier is divided into multiple amplifier sections with different gain values. Each section processes a portion of the input signal, allowing the chopper circuitry to be applied selectively to certain sections rather than the entire signal path. This segmentation reduces the overall output ripple while maintaining offset voltage reduction benefits.
Solution Approach 2:
Different amplifier sections are assigned different gain characteristics tailored to specific signal components. The chopper circuitry is locally applied to sections where it provides the most benefit, while other sections maintain continuous operation to avoid generating ripple. This local optimization balances offset reduction with ripple minimization.
2Measurement precision
If chopper circuitry is added to reduce input offset voltage, then input offset voltage is reduced, but device complexity increases
Solution Approach 1:
The amplifier sections are designed to serve multiple functions: they provide both signal amplification and selective chopper circuitry integration. The same amplifier structure can operate with or without chopper circuitry engaged, allowing a single design to handle multiple operational modes and reducing overall system complexity.
Solution Approach 2:
The chopper circuitry is implemented in a dynamic manner where different amplifier sections can be selectively enabled or disabled based on signal conditions. This dynamic configuration allows the system to adapt to different operating requirements without requiring a completely different circuit design for each scenario.
3Object-generated harmful factors
If multiple amplifier sections with different gains are used, then output ripple is reduced, but device complexity increases
Solution Approach 1:
Rather than applying chopper circuitry to all amplifier sections, the invention uses partial action by selectively enabling chopper circuitry only in specific sections where it provides the most benefit. This partial application reduces output ripple effectively while avoiding the complexity increase that would result from implementing chopper circuitry throughout the entire amplifier.
Data Source
AI summary
Apparatus and methods for chopper amplifiers are provided herein. In certain configurations, a chopper amplifier includes at least one differential transistor bank including a selection circuit and a plurality of transistors. The selection circuit can select a first portion of the transistors for operation in a first transistor group and a second portion of the transistors for operation in a second transistor group. During calibration, the chopper amplifier's input offset can be observed for different transistor configurations of the differential transistor banks. Although the transistors of a particular bank can be designed to have about the same drive-strength and/or geometry, the chopper amplifier can have a different input offset in different transistor configurations due to manufacturing mismatch between transistors, such as process variation. The chopper amplifier can be programmed to operate with the selected transistor configurations of the differential transistor banks to provide the amplifier with low input offset.