Negative-Capacitance Comparator for High-Frequency Latching
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Solution Overview
Problem
Sigma-delta modulators face limitations when operated at very high frequencies, such as greater than 5 GHz, due to challenges in achieving high speed, high accuracy, and large bandwidth in analog-to-digital converters for applications like analog and digital radio, base stations, and radar.
Innovation Solution
Incorporating negative capacitance circuitry to cancel output parasitic capacitance in comparators, allowing for shorter latching access times and enabling operation at higher frequencies, thereby increasing throughput by processing samples at higher frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If sigma-delta modulators are operated at very high frequencies (greater than 5 GHz), then throughput and processing speed are improved, but parasitic capacitance limits the maximum operating frequency and increases access time
Solution Approach 1:
The patent converts the harmful parasitic capacitance into a beneficial effect by generating a negative capacitance signal that mirrors and inverts the parasitic capacitance behavior. This negative capacitance is injected into the comparator output to cancel the parasitic effects, thereby reducing access time and enabling higher operating frequencies beyond the conventional 5 GHz limit
Solution Approach 2:
The patent introduces an intermediary negative capacitance circuit that acts as a mediator between the parasitic capacitance and the comparator operation. This intermediary circuit generates the compensating signal that interacts with the parasitic capacitance to neutralize its harmful effects, allowing the system to operate at higher frequencies without the usual time penalty
2Productivity
If negative capacitance circuitry is added to cancel parasitic capacitance, then access time is reduced and operating frequency is increased, but device complexity increases
Solution Approach 1:
The negative capacitance circuit is designed to perform multiple functions simultaneously: it cancels parasitic capacitance effects, extends the operating frequency range, and maintains compatibility with existing sigma-delta modulator architectures. This multi-functionality justifies the added complexity by delivering multiple performance benefits from a single circuit addition
Solution Approach 2:
The patent changes the electrical parameters of the comparator system by introducing negative capacitance, which fundamentally alters the time-frequency characteristics of the circuit. This parameter change enables the system to operate in a previously unreachable frequency regime, improving productivity despite the increased circuit complexity
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
The use of negative capacitance circuitry significantly reduces access time, enabling the comparator to operate at higher frequencies and achieve greater throughput, effectively addressing the limitations of sigma-delta modulators at high frequencies.
Implementation Method 1
generating a negative capacitance signal that is inverted and equal to the parasitic capacitance
Data Source
AI summary
A high-speed comparator circuit is provided. The circuit includes an amplifier portion, a latch portion, and a negative capacitance portion. The amplifier portion includes an input coupled to receive an analog signal and an output. The latch portion is coupled to the amplifier portion. The latch portion is configured to provide at the output a digital value based on the analog signal. The negative capacitance portion is coupled to the output. The negative capacitance portion is configured to cancel parasitic capacitance coupled at the first output.