Sample-and-Hold Amplifier Gain Switching for Faster Settling
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Solution Overview
Problem
Sample and hold circuits face challenges in achieving high resolution output signals due to long charge/discharge times caused by high operational amplifier gain, which can result in output not returning to differential zero within the clock period, leading to operational issues and increased chip area when attempting to address this with larger switches.
Innovation Solution
A signal sampling apparatus with a gain controller that adjusts the operational amplifier's gain in the sample mode to reduce charge/discharge time, allowing the output to return to differential zero within the clock period without compromising resolution, by using switches to control the gain of the operational amplifier.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the operational amplifier gain is increased to provide high resolution output signals, then the measurement precision is improved, but the charge/discharge time increases causing the output to not return to differential zero within the clock period
Solution Approach 1:
The patent applies dynamics by making the operational amplifier gain adjustable rather than fixed. The gain controller dynamically changes the gain based on the operational mode (sample mode vs. hold mode), allowing high gain during hold mode for resolution and reduced gain during sample mode for fast charge/discharge, thus resolving the time-resolution contradiction
Solution Approach 2:
The patent changes the gain parameter of the operational amplifier based on operational mode. By using the gain controller to adjust the gain according to whether the circuit is in sample or hold mode, the system optimizes both charge/discharge time and resolution without compromise
2Loss of time
If the switch size is increased to reduce charge/discharge time, then the charge/discharge time is reduced, but the chip area increases raising costs
Solution Approach 1:
Instead of changing the physical size of switches, the patent changes the gain parameter of the operational amplifier. This parameter change allows the same-sized switches to achieve faster charge/discharge by reducing the time constant through gain adjustment, avoiding the area penalty of larger switches
Data Source
AI summary
A signal sampling apparatus for generating an output signal according to an input signal is disclosed. The signal sampling system includes a sample and hold circuit and a gain controller. The sample and hold circuit is used for sampling the input signal to generate a sample signal in a sample mode, and the sample and hold circuit includes an amplifier having a gain for generating the output signal according to the sample signal in a hold mode. The gain controller is coupled to the amplifier for adjusting the gain in the sample mode.