High-speed internal hysteresis comparator
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Solution Overview
Problem
High-speed comparative circuits in digital circuits, such as A/D converters and high-speed receivers, face challenges with high power consumption, increased circuit area, and costs due to the need for high current sources or additional buffers to accurately compare signals at high transmission speeds.
Innovation Solution
A high-speed internal hysteresis comparator is designed with a differential amplifier and impedance supply units, which include transistors and resistances, to provide an inductive load at the output terminal, increasing high-frequency gain and response speed without the need for increased current sources or pre-buffers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the current of the current source in the comparator is increased to correctly output comparing result for high-speed signals, then the comparing accuracy is improved, but the power consumption increases
Solution Approach 1:
The patent changes the impedance parameter of the active load from resistive to inductive characteristics. By introducing inductive impedance (through coupled inductors or artificial inductance circuits), the comparator achieves higher comparing accuracy for high-speed signals without increasing current source magnitude, thus avoiding increased power consumption. The inductive impedance provides frequency-dependent gain enhancement specifically for high-frequency differential input signals.
Solution Approach 2:
The patent employs dynamic impedance adjustment by using active circuits (such as controlled current sources or transconductance amplifiers) to simulate inductive load characteristics. This dynamic approach allows the comparator to adapt its impedance characteristics to the high-speed signal conditions, providing the necessary gain enhancement only when needed for high-frequency operation, rather than requiring continuously high current consumption.
2Speed
If an additional pre-buffer is disposed in the comparator circuit to improve high-speed comparing performance, then the response speed is improved, but the circuit area increases
Solution Approach 1:
The patent merges the pre-buffer function into the existing differential amplifier stage by configuring the active load with inductive impedance. This integration allows the same circuit block to perform both differential amplification and high-speed signal conditioning functions, eliminating the need for a separate pre-buffer stage and thus avoiding additional circuit area while maintaining improved response speed for high-frequency signals.
Solution Approach 2:
The inductive active load serves multiple functions simultaneously: it provides the necessary gain for high-speed comparing, enhances the frequency response of the differential amplifier, and acts as an impedance transformation element. This multi-functionality eliminates the need for dedicated pre-buffer circuits, achieving high-speed performance without increasing circuit area.
3Measurement precision
If the current source current is increased to handle high transmitting speed signals, then the signal comparing accuracy is improved, but the cost increases
Solution Approach 1:
The patent changes the impedance parameter of the active load to inductive characteristics, which provides frequency-dependent gain enhancement. This parameter change allows the comparator to achieve high signal comparing accuracy for high-speed signals using the same current source, avoiding the need for high-current designs and the associated increased manufacturing costs.
Data Source
AI summary
A high speed internal hysteresis comparator is provided. Impedance supply units are disposed at control terminals of transistors of an active load of a differential amplifier of the high-speed hysteresis comparator, such that a gain when the transistors operate in an active region and a responding speed of the high-speed hysteresis comparator are increased.