Op Amp Offset Trim Circuit for Temperature Drift Compensation
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Solution Overview
Problem
Operational amplifiers (op amps) experience temperature-dependent offset voltage drift, leading to increased errors in output as temperature changes, as existing calibration and trimming methods are only effective at the temperature at which they were performed, failing to maintain constant offset voltage across varying ambient temperatures.
Innovation Solution
A method and circuit that generate a temperature-dependent error correction current to minimize the difference in current flow through transistors, injecting this correction current into the emitter terminal of specific transistors to counteract temperature effects on offset voltage errors, using a combination of transistors and error correction circuits to maintain a relatively constant offset voltage over temperature variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If calibration/trimming is performed at room temperature, then offset voltage error is minimized at that temperature, but offset voltage drift increases as temperature changes
Solution Approach 1:
The patent implements dynamic offset compensation by making the compensation current adjustable and temperature-dependent. The circuit transitions from static room-temperature calibration to continuous dynamic adjustment, where the compensation current is modulated based on temperature variations to maintain accurate offset compensation across the full operating temperature range
Solution Approach 2:
The patent changes the parameter of compensation current from a fixed DC value to a temperature-dependent variable current. By making the compensation current a function of temperature, the system adapts to temperature variations and maintains offset voltage accuracy dynamically throughout the operating temperature range
2Measurement precision
If offset voltage is compensated at a single temperature, then accuracy is achieved at that temperature, but error increases with temperature variations
Solution Approach 1:
The system transitions from static single-temperature compensation to dynamic multi-temperature adaptation. The compensation mechanism continuously adjusts its behavior based on temperature conditions, enabling the circuit to maintain accuracy across varying temperature environments rather than being optimized for a single operating point
Solution Approach 2:
The compensation current parameter is transformed from a fixed value to a temperature-dependent variable. This parameter change enables the circuit to adapt its compensation behavior to different temperature conditions, significantly improving temperature range adaptability while maintaining output accuracy
Data Source
AI summary
Disclosed embodiments include a method for reducing amplifier offset drift comprised of receiving a first differential input signal at a first transistor base terminal and a second differential input signal at a second transistor base terminal, coupling the collector of the first transistor to the emitter of a third transistor and the emitter of the second transistor to the emitter of a fourth transistor, then coupling the base of the third transistor to the base of the fourth transistor. The method is also comprised of coupling the collector of the fourth transistor to an output terminal, generating a temperature dependent error correction current to minimize the difference in the amount of current flowing through the third transistor and the amount of current flowing through the fourth transistor, then injecting the error correction current into the emitter terminal of at least one of either the third transistor or the fourth transistor.