Comparator Input Charge Injection for Kickback Reduction
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Solution Overview
Problem
Comparators experience reduced accuracy due to kickback effects caused by voltage variations across source and drain voltage-controlled switches, which are coupled through parasitic capacitances, and exacerbated by non-zero output impedance of drivers.
Innovation Solution
Incorporating a preamplifier with DC bias current in the comparator circuit to neutralize the charge produced across the input differential pair through equivalent charge injection by voltage-controlled units, similar to the input differential pair, thereby reducing kickback effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If voltage controlled switches are used in the comparator input stage, then the comparator can function as a basic building block for circuits such as ADCs and memories, but large voltage variations are kicked back to the input through parasitic capacitances reducing accuracy
Solution Approach 1:
The patent applies preliminary anti-action by introducing a preamplifier stage before the main comparator that anticipates and counteracts the kickback effect. The preamplifier with DC bias current generates an opposing signal that neutralizes the voltage variations kicked back through parasitic capacitances, thereby maintaining input voltage accuracy while preserving comparator functionality in ADCs and memories
Solution Approach 2:
The patent uses an intermediary preamplifier stage between the input voltage source and the main comparator input. This intermediary component buffers the kickback effect by absorbing voltage variations through its DC bias current configuration, preventing them from reaching the sensitive comparator input while allowing the comparator to maintain its essential function in various circuits
2Ease of operation
If input voltage driver or reference voltage driver with non-zero output impedance is used, then the driver can provide voltage control to the differential pair, but the input voltage of the comparator changes reducing accuracy
Solution Approach 1:
The preamplifier acts as an intermediary between the voltage driver and the comparator input, isolating the driver's non-zero output impedance from affecting the comparator input voltage. The preamplifier with DC bias current maintains a stable virtual ground potential, preventing impedance-induced voltage variations from reaching the comparator while preserving the driver's voltage control capability
Solution Approach 2:
The patent implements beforehand cushioning by using the preamplifier with DC bias current to create a buffered input stage that absorbs and dampens voltage variations before they can affect the comparator. This cushioning effect compensates for the driver's output impedance in advance, maintaining input voltage stability while allowing easy voltage control
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively reduces kickback voltage from 16 mV to 5 mV without requiring additional DC bias current, enhancing the accuracy and robustness of comparator outputs by minimizing the impact of process and temperature variations.
Implementation Method 1
a charge is produced across the same owing to the coupling capacitances of the differential pair. The voltage controlled units in turn produce equivalent charge which neutralizes the charge produced across the input differential pair
Data Source
AI summary
The present disclosure relates to reduction in the effect of kickback in comparators by means of charge injection implemented by means of voltage controlled switches with attributes similar to those of an input differential pair. The voltage controlled switches produce charge to neutralize the charge loss during latching of inputs in the comparator.