This technology provides the design for a fully differential, high-pass switched-capacitor filter, or "mirrored integrator", which is a significant element of the previously proposed, improved analog to digital converter (ADC) architecture.
The new ADC architecture features reduced noise and power consumption, increased resolution and stability, and smaller device size.
The essence of the new ADC architecture is to control circuit noise by shifting the input signal to the upper frequency range of the spectrum. The output signal is then passed through a high-pass filter (in opposition to a conventional sigma-delta converter in which the signal is passed through a low-pass filter). After filtering, the signal is decimated by employing the procedure used in conventional sigma-delta converters. The noise-shaping property of the new architecture "pushes" noise toward the low-frequency portion of the spectrum, which is already cluttered with the 1/f noise, DAC non-linearity and op amp and quantizer harmonic distortion. All this low-frequency noise is then filtered out by the high-pass filter, which is the subject of the current invention.
This invention will compete with the conventional sigma delta designs for high resolution applications because of both dynamic range and power reasons, and with other ADC types in certain applications because of its low power requirements. Compared to a conventional sigma delta ADC, our invention has the following advantages:
Improved dynamic range, because higher order DAC will be allowed and a dramatic reduction in 1/f noise.
Reduced offset error and drift.
Dramatically lower power consumption per bit, allowing the design tradeoff of over sampling rate for resolution.
Smaller size circuits because smaller input transistors can be used, because of the noise reduction features of the design.
Reduced analog noise.
Reduced operational amplifier analog noise (thermal + 1/f).
Suppression of DAC nonlinearity.
Improved attenuation of the DAC's DC offset.