Latch-Based Op-Amp Offset Compensation With Lower Noise
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Solution Overview
Problem
Existing operational amplifiers face challenges in minimizing power consumption and noise generation, particularly in integrated circuits, due to offset voltage issues and the need for complex capacitor configurations and continuous switching operations, which can degrade circuit performance and induce noise.
Innovation Solution
An operational amplifier design incorporating a differential amplification circuit and offset memory using a latch circuit to store and manage offset voltage, allowing for accurate offset modification without continuous switching, thereby reducing power consumption and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If continuous switching operation is used to compensate offset voltage, then offset compensation is achieved, but noise is induced and circuit performance is degraded
Solution Approach 1:
The patent implements periodic switching operation instead of continuous switching. The switching occurs only during specific phases (sampling phase and hold phase) rather than continuously, which reduces noise generation while still achieving offset compensation. The periodic nature of the switching allows the circuit to settle between switching events, minimizing noise impact on the output signal.
2Measurement precision
If capacitor configuration is used for offset compensation, then offset voltage is removed, but device complexity increases
Solution Approach 1:
The patent combines the offset compensation function with the existing operational amplifier structure by integrating switching elements and capacitors directly into the amplifier circuit. The sampling capacitor is merged with the compensation mechanism, eliminating the need for separate external capacitor configurations. This integration reduces device complexity while maintaining offset compensation effectiveness.
3Measurement precision
If external adjustments are used for offset compensation, then offset accuracy is improved, but test time increases
Solution Approach 1:
The patent implements self-calibration functionality within the operational amplifier circuit. The circuit automatically performs offset compensation through internal switching and capacitor charging/discharging operations without requiring external adjustment mechanisms. This self-service approach eliminates the need for manual or external calibration procedures, significantly reducing test time while maintaining high offset accuracy.
4Measurement precision
If switching operation is used for offset sampling, then offset voltage is captured, but power consumption increases
Solution Approach 1:
The patent uses periodic switching operation where the switches are activated only during specific sampling intervals rather than continuously. During the sampling phase, switches close to capture the offset voltage on the capacitor. During the hold phase, switches open to maintain the stored voltage. This periodic action significantly reduces power consumption compared to continuous switching while still achieving accurate offset voltage sampling.
Data Source
AI summary
An operational amplifier capable of suppressing power consumption and noise generation includes an offset modifier including a differential amplification circuit, and an offset memory for storing an offset voltage using a latch circuit. The differential amplification circuit includes first and second NMOS transistors connected to an input terminal, first and second PMOS transistors respectively connected to drains of the first and second NMOS transistors, a third NMOS transistor connected to sources of the first and second NMOS transistors, a third PMOS transistor connected to a source of the second PMOS transistor, a fourth NMOS transistor connected to the third PMOS transistor, to form an output to be applied to the offset memory, and left and right modification blocks each connected to an associated one of the first and second NMOS transistor in parallel.