Active RC Resonator Tuning With Parasitic Cancellation
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Solution Overview
Problem
The Q factor of active RC resonators in analog-to-digital converters is degraded by parasitic components introduced by digitally-controlled MOSFET switches, which are used to tune the resonators for a wide range of frequencies, making it difficult to achieve a desirable Q factor greater than 30 at high resonance frequencies like 1 GHz.
Innovation Solution
The introduction of cancelling capacitors that generate a negative current to counteract the effects of parasitic capacitance and resistance, specifically coupling cancelling capacitors to match and exceed the parasitic components, thereby enhancing the Q factor of the active RC resonator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If digitally-controlled MOSFET switches are used to tune the resonator for a wide range of frequencies, then the frequency tuning range is improved, but the Q factor is degraded due to parasitic components
Solution Approach 1:
The patent converts the harmful parasitic capacitance and resistance introduced by MOSFET switches into beneficial effects by introducing cancelling capacitors that generate negative current to counteract the parasitic components. The parasitic elements are not removed but are instead compensated for through carefully designed cancelling circuits, transforming the harmful effect into a manageable parameter.
Solution Approach 2:
The patent introduces cancelling capacitors as intermediary elements between the MOSFET switches and the resonator circuit. These cancelling capacitors act as mediators that generate compensating currents to offset the parasitic effects, allowing the MOSFET switches to remain in the circuit for frequency tuning without degrading the Q factor.
2Reliability
If MOSFET switches are made larger to reduce parasitic resistance, then the Q factor is improved, but the parasitic capacitance increases which degrades the Q factor
Solution Approach 1:
The patent converts the harmful parasitic capacitance into a beneficial parameter by designing cancelling capacitors that specifically target and compensate for the parasitic capacitance. Rather than trying to eliminate the parasitic capacitance by making switches smaller, the patent uses the cancelling capacitors to generate negative current that counteracts the capacitive effect.
Solution Approach 2:
The patent changes the electrical parameters of the circuit by introducing cancelling capacitors with specific capacitance values that are tuned to match the parasitic capacitance of the MOSFET switches. This parameter matching allows for optimal cancellation of the parasitic effects across different switching states.
Data Source
AI summary
An active RC resonator includes a first operational amplifier having first and second inputs and first and second outputs, a second operational amplifier having first and second inputs and first and second outputs, a first resistor coupled between the first input of the first operational amplifier and the second output of the second operational amplifier, a second resistor coupled between the second input of the first operational amplifier and the first output of the second operational amplifier, a third resistor coupled between the first output of the first operational amplifier and the first input of the second input of the second operational amplifier, a fourth resistor coupled between the second output of the first operational amplifier and the second input of the second operational amplifier, and at least one of 1) a first capacitor coupled between the first input of the first operational amplifier and the first output of the second operational amplifier, and a second capacitor coupled between the second input of the first operational amplifier and the second output of the second operational amplifier, 3) a third capacitor coupled between the second output of the first operational amplifier and the first input of the second operational amplifier, and a fourth capacitor coupled between the first output of the first operational amplifier and the second input of the second operational amplifier.