Display Device Offset Voltage Control via Chopper Signal

The patent changes the operating parameters of the operational amplifier by dynamically adjusting the tail current based on the output signal polarity. When the output signal is positive, the tail current is increased; when negative, the tail current is decreased. This parameter adjustment allows the use of smaller transistors while maintaining low offset voltage performance, thereby reducing the source driver size without sacrificing measurement precision.

The patent implements periodic switching of the tail current direction and magnitude based on the polarity of the output signal. The current mirror circuit periodically reverses the current flow direction, and the chopper stabilization technique periodically swaps the roles of input terminals. This periodic action enables smaller transistors to achieve the same offset voltage performance as larger static transistors, resolving the contradiction between precision and size.

The patent replaces the traditional mechanical approach of using large physical transistors to reduce offset voltage with an electrical control mechanism. The chopper control circuit dynamically adjusts the tail current and swaps terminal roles to achieve offset voltage cancellation, substituting the mechanical size-based solution with an intelligent electrical control system. This allows standard-sized transistors to perform as if they were larger, eliminating noise while maintaining compact chip size.

The operational amplifier circuit performs self-correction of offset voltage through the chopper control mechanism. The circuit automatically detects the output polarity and adjusts the tail current direction and magnitude accordingly, eliminating the need for external calibration or large transistor designs. This self-service capability allows standard transistors to achieve low offset voltage performance dynamically, preventing noise generation while maintaining small chip size.