Passive MOSFET Mixer Biasing for Temperature-Stable Linearity
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Solution Overview
Problem
Existing passive mixer circuits face a decrease in linearity of frequency conversion due to temperature fluctuations, which affect the optimal gate and source-drain bias voltages of MOSFETs.
Innovation Solution
A passive mixer circuit design that includes a bias generation section with a sub-MOSFET of the same type as the main MOSFET, utilizing a voltage follower circuit and operational amplifier to generate and supply gate and source-drain bias voltages based on the sub-MOSFET's gate and source voltages, ensuring the main MOSFET operates with stable bias despite temperature changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fixed gate bias voltage and source-drain bias voltage are applied to the MOSFET, then the MOSFET can function as a switch, but the linearity of frequency conversion decreases when temperature changes occur
Solution Approach 1:
The patent dynamically adjusts the gate bias voltage and source-drain bias voltage based on temperature changes. By detecting temperature variations and相应地 changing the bias voltage parameters, the circuit maintains optimal MOSFET switching characteristics across different temperature conditions, thereby preserving frequency conversion linearity
Solution Approach 2:
The patent implements a feedback mechanism where temperature information is detected and used to adjust the bias voltages. This closed-loop control ensures that the bias voltages are continuously optimized according to actual temperature conditions, preventing degradation of frequency conversion performance
2Reliability
If bias voltages are adjusted to maintain linearity, then frequency conversion performance improves, but circuit complexity increases
Solution Approach 1:
The patent introduces a voltage divider circuit as an intermediary component that generates the bias voltages. This simple passive circuit structure avoids the need for complex active control circuits while still achieving temperature-compensated bias voltage generation, thus minimizing the increase in circuit complexity
Data Source
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AI summary
A passive mixer circuit includes a high-frequency terminal, a low-frequency terminal, a main MOSFET to which a local oscillation frequency signal is input, and a bias generation section, in which the bias generation section includes a sub-MOSFET of a same type as the main MOSFET, a voltage follower circuit including an operational amplifier, and a resistance element, a drain and a gate of the sub-MOSFET are shorted and directly or indirectly receive an output from the voltage follower circuit, a reference voltage is input to a non-inverting input terminal of the operational amplifier, a gate bias voltage based on a gate voltage of the sub-MOSFET is supplied to a gate of the main MOSFET, and a source-drain bias voltage based on a source voltage of the sub-MOSFET is supplied to a source or a drain of the main MOSFET.