Current-Mirror Constant Resistance Circuit for Accurate On-Chip Matching
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Solution Overview
Problem
On-chip resistors in integrated circuits exhibit significant resistance variations due to process and temperature variations, leading to increased gain errors and poor linearity, especially at high frequencies, making it difficult to achieve precise impedance matching in communications and video devices.
Innovation Solution
A system comprising a first transistor interconnected between two nodes, a diode-connected second transistor forming a current mirror, and a voltage divider configured in parallel to provide a substantially constant resistance, with a current source controlling the current through the second transistor to set the resistance to a desired value, using a control circuit with a replica circuit and a constant resistor to adjust the resistance value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If on-chip resistors are used in integrated circuits, then the circuit can be integrated and compact, but the resistance value varies significantly due to process and temperature variations
Solution Approach 1:
The patent changes the operating parameters of transistors to achieve constant resistance. By controlling the current through the transistor and operating it in the triode region with specific voltage and current relationships, the transistor exhibits constant resistance behavior that is insensitive to process and temperature variations, thus achieving both integration and precision.
Solution Approach 2:
The patent employs feedback mechanisms where the current through the transistor is controlled based on voltage measurements, and the resistance is continuously adjusted to maintain a constant value. The control circuit monitors the resistance and adjusts the current accordingly to compensate for process and temperature variations.
2Manufacturing precision
If external precision resistors are used to control resistance value variations, then resistance accuracy improves, but the physical size and cost of the circuit increases
Solution Approach 1:
The patent replaces physical resistors with an electronic system using transistors operating in the triode region. This substitution eliminates the need for external precision resistors while achieving the same or better resistance precision through electronic control of current and voltage, thereby reducing circuit size and cost.
Solution Approach 2:
The patent uses dynamic parameter control of transistor current and voltage to achieve constant resistance, replacing static resistor values with dynamically adjustable parameters that can be precisely controlled through electrical signals, achieving high precision without external components.
3Manufacturing precision
If trimming or tuning methods are implemented to control resistance, then resistance accuracy improves, but the device complexity and cost increase
Solution Approach 1:
The patent implements a self-regulating system where the transistor circuit automatically adjusts its own operating parameters to maintain constant resistance. The control circuit continuously monitors and adjusts the current without requiring external trimming or tuning, making the system self-correcting and reducing overall device complexity.
4Area of stationary object
If on-chip resistors are used, then integration is achieved, but linearity is poor particularly at high frequencies
Solution Approach 1:
The patent operates the transistor in the triode region where the relationship between current and voltage can be controlled to achieve linear behavior. By carefully selecting operating points and controlling the current through the transistor, the system achieves improved linearity at high frequencies compared to traditional on-chip resistors.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution achieves a high degree of resistance accuracy (±5%) and linearity, effectively compensating for process and temperature variations, while avoiding the need for bulky and expensive external resistors, and can be implemented in a compact integrated circuit.
Implementation Method 1
a second transistor, the second transistor being diode connected, the first transistor and the second transistor forming a current mirror
Implementation Method 2
A voltage divider is coupled to provide a portion of a voltage associated with the first transistor to the second transistor, the voltage divider being configured parallel to the first transistor to provide a substantially constant resistance
Implementation Method 3
A voltage divider is coupled to provide a portion of a voltage associated with the first transistor to the second transistor
Implementation Method 4
A current source is coupled to the second transistor, the current source being controlled to draw an amount of current through the second transistor to set the substantially constant resistance substantially equal to the desired substantially constant resistance
Data Source
AI summary
A system for providing a desired substantially constant resistance includes a first transistor interconnected between a first node and a second node. The system also includes a second transistor, the second transistor being diode connected, the first transistor and the second transistor forming a current mirror. A voltage divider is coupled to provide a portion of a voltage associated with the first transistor to the second transistor, the voltage divider being configured parallel to the first transistor to provide a substantially constant resistance between the first node and the second node. A current source is coupled to the second transistor, the current source being controlled to draw an amount of current through the second transistor to set the substantially constant resistance substantially equal to the desired substantially constant resistance.