Complementary Transistor Termination Circuit for Adjustable Impedance
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Solution Overview
Problem
High-frequency signal propagation in digital and communication systems is hindered by impedance discontinuities, leading to significant signal loss and distortion due to mismatched impedances between transmission lines and receivers, which existing technologies fail to adequately address.
Innovation Solution
A termination circuit with a variable resistance network comprising complementary N-channel and P-channel transistors, whose resistance remains constant despite varying drain-to-source voltages, allowing for adjustable impedance matching through a digital-to-analog converter output signal, thereby reducing signal reflections and improving bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If discrete resistive elements are used for impedance matching, then impedance matching is achieved, but product size and manufacturing cost increase
Solution Approach 1:
The patent combines multiple functions (impedance matching, signal termination, biasing) into a single integrated transistor circuit block, eliminating the need for separate discrete resistive elements. The complementary transistor pair with controlled gate voltages provides both the termination resistance and the biasing function that would otherwise require external components.
Solution Approach 2:
The patent replaces physical discrete resistive elements with an electronic transistor-based resistance network. The effective resistance is controlled through electrical means (gate voltages) rather than through physical component selection and assembly, enabling dynamic adjustment and integration.
2Reliability
If discrete resistive elements are used for impedance matching, then impedance matching is achieved, but manufacturing and assembly cost increase
Solution Approach 1:
The patent combines multiple functions (impedance matching, signal termination, biasing) into a single integrated transistor circuit block, eliminating the need for separate discrete resistive elements. The complementary transistor pair with controlled gate voltages provides both the termination resistance and the biasing function that would otherwise require external components.
Solution Approach 2:
The patent replaces physical discrete resistive elements with an electronic transistor-based resistance network. The effective resistance is controlled through electrical means (gate voltages) rather than through physical component selection and assembly, enabling dynamic adjustment and integration.
3Reliability
If conventional termination circuits are used, then impedance matching is provided, but signal fidelity deteriorates due to reflections
Solution Approach 1:
The patent employs a dynamic resistance network where the effective termination resistance can be adjusted by controlling the gate voltages of the complementary transistors. This dynamic capability allows the termination resistance to be optimized for different signal conditions and frequencies, improving impedance matching and reducing reflections compared to fixed resistance circuits.
Solution Approach 2:
The patent changes the electrical parameters (gate voltages) of the transistor circuit to control the effective termination resistance. By adjusting the gate voltages, the resistance network can be tuned to match the characteristic impedance of the transmission line, thereby minimizing signal reflections and improving signal fidelity.
4Reliability
If the resistance network is made adjustable, then impedance matching improves, but circuit complexity increases
Solution Approach 1:
The patent designs the transistor circuit to perform multiple functions simultaneously: providing termination resistance, establishing bias points for other circuit elements, and enabling adjustable impedance matching. This multi-functionality reduces the need for separate dedicated circuits for each function, thereby limiting the increase in overall circuit complexity.
Data Source
AI summary
In one implementation, a termination circuit may include a variable resistance circuit that comprises a resistance network in which the resistance of a parallel combination of two complementary transistors of opposite types is substantially independent of the drain-to-source voltages of the transistors when the gate-to-source voltages of the transistors are substantially equal in magnitude and opposite in sign. In various examples, the network may include a resistor in parallel and/or series with the transistors. Some implementations may adjust a resistance of the network in response to a digital-to-analog converter output signal. In another implementation, an integrated circuit may include a termination stage with an integrated resistor in parallel or series with a circuit having a tunable impedance. In an illustrative embodiment, relative channel width of the first and second transistors may be selected to realize substantially complementary characteristics for drain-to-source voltage vs. drain-to-source resistance.