Controlled Transistor On-Resistance for Temperature Compensation
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Solution Overview
Problem
Conventional high-frequency broadband amplifiers with feedback resistors exhibit significant gain variation over temperature, making it difficult to create effective temperature-dependent feedback resistors to compensate for these variations.
Innovation Solution
A controlled transistor on-resistance with predefined temperature dependence is implemented using a composite resistance created from multiple transistors, where the on-resistance varies with gate voltage in a closed loop, providing a predefined temperature profile and improving linearity by stacking transistors and connecting them in series with a normal resistor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a feedback resistor is used in a broadband amplifier, then the amplifier can operate at high frequencies, but the gain varies significantly over temperature
Solution Approach 1:
The patent applies dynamics by making the feedback resistance variable rather than fixed. The feedback resistor is replaced with a controllable resistance element (such as a transistor operating in the triode region) whose resistance can be dynamically adjusted based on temperature. This dynamic adjustment allows the feedback network to compensate for temperature-induced gain variations while maintaining high-frequency operation.
Solution Approach 2:
The patent changes the resistance parameter of the feedback element based on temperature. By using a temperature-dependent biasing scheme or a controlled voltage source, the resistance value is modified as temperature changes, thereby compensating for the gain variations that would otherwise occur in the amplifier circuit.
2Stability of the object's composition
If a temperature-dependent feedback resistor is used to compensate for gain variation, then gain stability improves, but the device complexity increases
Solution Approach 1:
The patent applies self-service by designing a feedback resistance element that automatically adjusts its value in response to temperature changes without requiring external control circuits. For example, a transistor biased in the triode region naturally exhibits temperature-dependent resistance characteristics that can directly compensate for amplifier gain variations, eliminating the need for separate temperature sensing and control mechanisms.
Solution Approach 2:
The patent makes the feedback element serve multiple functions: it provides the necessary feedback for high-frequency operation and simultaneously acts as a temperature compensation mechanism. By selecting a device topology where the same component performs both roles, the circuit avoids the complexity of adding dedicated temperature compensation circuitry.
3Manufacturing precision
If multiple transistors are stacked to improve linearity, then the linearity improves, but the device area increases
Solution Approach 1:
The patent applies segmentation by dividing the feedback resistance function across multiple transistor devices rather than using a single large resistor. By stacking transistors in series, each contributing a portion of the total resistance, the circuit achieves improved linearity through the distributed structure while managing the area occupation through efficient vertical stacking rather than horizontal layout.
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
This solution effectively compensates for temperature-dependent gain variations, reducing overall gain variation over temperature, improving tolerance and linearity, and providing better immunity to process variations compared to common resistors.
Implementation Method 1
a controlled transistor on-resistance with predefined temperature dependence
Implementation Method 2
The variable current may be proportional to a temperature of the first circuit
Data Source
AI summary
An apparatus includes a first circuit and a second circuit. The first circuit may be configured to generate (i) a variable current and (ii) a constant current. The variable current may be proportional to a temperature of the first circuit. The second circuit may be configured to present a resistance through a plurality of first transistors between two ports in response to both the variable current and the constant current. The resistance may have a predefined dependence on the temperature.