Gain-Compensated CT Delta-Sigma Modulator for Limited Amplifier Gain
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Solution Overview
Problem
Continuous-time delta-sigma modulators (CTDSMs) face limitations in linearity and power consumption due to the linearity of the first integrator in its loop filter, particularly at high sampling frequencies, which affects their performance in broadband radio and radar applications.
Innovation Solution
Employing a single-stage inverter-based amplifier with gain compensation, utilizing a gain compensation circuit to enhance the signal-to-quantization-noise ratio (SQNR) while reducing power consumption by moving the gain compensation stage further in the signal chain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a single-stage inverter-based amplifier is used, then power consumption is reduced, but the amplifier gain is limited
Solution Approach 1:
The gain compensation function is segmented from the main amplifier and placed in a separate stage further down the signal chain. This allows the main amplifier to operate with lower power consumption while the dedicated compensation stage restores the required gain, resolving the contradiction between power consumption and amplifier gain.
Solution Approach 2:
A gain compensation circuit acts as an intermediary element that compensates for the limited gain of the single-stage amplifier. This intermediary component enables the system to achieve the required overall gain without increasing the power consumption of the main amplifier.
2Measurement precision
If gain compensation is applied early in the signal chain, then signal-to-quantization-noise ratio is improved, but power consumption increases
Solution Approach 1:
The gain compensation is applied at an optimal point in the signal chain where it most effectively improves the signal-to-quantization-noise ratio without requiring excessive power. By positioning the compensation stage further down the chain rather than at the beginning, the system achieves the necessary SQNR improvement with minimal additional power consumption.
3Power
If multi-stage amplifiers are used, then amplifier gain is improved, but device complexity increases
Solution Approach 1:
Instead of using a complex multi-stage amplifier architecture, the gain compensation function is segmented and placed in a separate, simpler stage further down the signal chain. This segmentation approach achieves the required overall gain while maintaining lower device complexity compared to traditional multi-stage amplifier designs.
Data Source
Figure 1A~1B
Figure 2
Figure 3
AI summary
A modulator circuit may include an integrator circuit and a gain compensation circuit. The integrator circuit may include a first amplifier including an input to receive a signal and an output to provide an inverted signal and a capacitor including a first terminal coupled to the input and a second terminal coupled to the output. The gain compensation circuit may include a second inverter amplifier including a gain input coupled to the output of the first amplifier and including a gain output; a first resistor including a first terminal coupled to the gain output and including a second terminal; and a second capacitor including a first terminal coupled to the second terminal of the first resistor and including a second terminal coupled to the gain input. The integrator circuit has a finite DC gain and the gain compensation circuit is configured to compensate for the finite DC gain.