Reducing Input Referred Thermal Noise Voltage in Dynamic Comparator

What is it about?

Thermal noise is an important consideration in ADC design, especially so in high resolution ADC, where the input referred thermal noise voltage of the comparator can reduce the effective resolution of the ADC by a few bits lower than the designed value. The comparator circuit proposed in this work will help alleviate this problem, without imposing large additional silicon area requirement compared to standard comparator.

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Photo by Alexandre Debiève on Unsplash

Photo by Alexandre Debiève on Unsplash

Why is it important?

The conventional method of reducing input referred thermal noise voltage in dynamic comparator is by increasing the load capacitor. This can be very challenging when very low input referred thermal noise is required, due to the large size of the required load capacitor of the comparator. Other than the increase in production cost due to increased silicon area, this large load capacitor will also impose a limitation on the applicability of the dynamic comparator in applications with tight form factor requirements such as image sensors. By reducing the required capacitor size, this work can provide a good solution to this problem.