Track-and-Hold Amplifier Isolation Circuit for Fast Low-Noise Settling
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In high frame rate and high resolution imaging applications, track-and-hold amplifiers face challenges with settling time, which affects performance, and mismatched settling times between amplifiers can introduce noise in signals. Reducing settling time through increased supply current or decreased sampling capacitor size either increases power consumption or kTC noise, respectively.
Innovation Solution
A track-and-hold amplifier with an isolation circuit that isolates transient current during the track phase, allowing for a settling time independent of the amplifier gain, achieved by selectively activating the isolation circuit and redirecting current from the track-and-hold capacitor to ensure constant current through the first transistor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If supply current is increased to reduce settling time, then settling time is reduced, but power consumption increases
Solution Approach 1:
The patent implements dynamic current steering by selectively activating isolation circuits (first and second isolation circuits) during different phases (track phase vs. hold phase). During the track phase, the isolation circuits are activated to steer current away from the track-and-hold capacitor, enabling fast settling. During the hold phase, the isolation circuits are deactivated to maintain the held value. This dynamic switching allows the system to achieve fast settling times without continuously consuming high power.
Solution Approach 2:
The patent extracts and isolates transient current from the main signal path by introducing isolation circuits that selectively connect or disconnect the track-and-hold capacitor from the amplifier output. The isolation circuits remove transient current effects during the track phase, allowing the settling time to be reduced without proportionally increasing the supply current, thus avoiding excessive power consumption.
2Loss of time
If sampling capacitor size is decreased to reduce settling time, then settling time is reduced, but kTC noise increases
Solution Approach 1:
The patent introduces isolation circuits as intermediary elements between the amplifier output and the track-and-hold capacitor. These isolation circuits mediate the charge transfer process by providing controlled connection and disconnection, enabling the system to use a smaller sampling capacitor for faster settling while the isolation circuits manage the charge transfer to minimize noise generation.
Solution Approach 2:
The patent uses dynamic switching of the isolation circuits to control when the track-and-hold capacitor is connected to or isolated from the amplifier. During the track phase, the capacitor is connected to track the input signal. During the hold phase, the capacitor is isolated to maintain the held value. This dynamic control allows smaller capacitor sizes without proportionally increasing noise, as the isolation circuits manage the charge transfer carefully.
Data Source
AI summary
Various embodiments of the present technology may comprise methods and apparatus for a track-and-hold amplifier configured to sample and amplify an analog signal. Methods and apparatus for a track-and-hold amplifier according to various aspects of the present invention may comprise an isolation circuit configured to isolate transient current in a track-and-hold capacitor during a track phase. According to various embodiments, selective activation of the isolation circuit provides a settling time that is independent of the gain of the amplifier.