Amplifier Offset Compensation Circuit Without Ground-Referenced Supply
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Solution Overview
Problem
Conventional circuits for compensating offset voltage and DC components in amplifiers suffer from limited common-mode input signal range, non-linear behavior, increased distortion, and noise due to ground-referenced power supplies, which restrict the dynamic voltage range and linear performance.
Innovation Solution
The circuit separates the power supply contacts from ground potential, using a first voltage source without reference to ground or external potential, positioning the measurement signal at the optimal operating point within the linear range, and optionally adding a second power source to compensate for offset voltage and DC components, ensuring the dynamic voltage range is not referenced to ground, thus eliminating DC components and internal offsets from the amplified signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an external offset voltage is supplied to compensate internal offset voltage and DC components, then the offset compensation function is achieved, but the common-mode input signal range is limited and the dynamic voltage range is reduced
Solution Approach 1:
The power supply system is segmented into two independent parts: a first voltage source providing the main supply voltage Vcc and a second voltage source providing the adjustable offset voltage Voffset. Both sources are galvanically separated from ground potential, allowing independent adjustment of the offset voltage without affecting the common-mode input signal range of the amplifier.
Solution Approach 2:
A galvanic separation (isolation) is introduced between the power supply system and ground potential, acting as an intermediary that allows the amplifier to operate with an elevated common-mode voltage level. This isolation enables the amplifier to handle larger signal swings while maintaining proper offset compensation.
2Measurement precision
If the offset voltage is adjusted to compensate DC components, then the DC accuracy is improved, but the DC operation point shifts causing non-linear behavior and increased distortion
Solution Approach 1:
The second voltage source is made adjustable, allowing the offset voltage Voffset to be dynamically tuned to the specific amplifier and operating conditions. This dynamic adjustment capability enables optimization of both DC accuracy and linearity, allowing the user to find the optimal operating point that minimizes distortion while maintaining proper offset compensation.
3Device complexity
If ground-referenced power supplies are used, then the circuit design is simplified, but noise is introduced and the DC operation point becomes unstable
Solution Approach 1:
Galvanic separation is introduced as an intermediary between the power supplies and ground, blocking the transmission of ground potential variations and associated noise to the amplifier's DC operation point. This isolation maintains circuit simplicity while eliminating the harmful effects of ground-referenced power supplies.
Data Source
AI summary
A circuit for compensating an offset voltage in an amplifier or a DC component in a signal supplied to the amplifier comprises the amplifier and a first voltage source. The amplifier has at least one measurement signal port and at least two contacts for a supply voltage. Each of two contacts is connected to a different terminal of the first voltage source. The potential at each contact is separated from a ground potential and from an external supply potential.