Current-Reuse FET Amplifier Bias Control for Stable Drain Current
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Solution Overview
Problem
Current GaAs-based FET amplifiers in depression mode face challenges in maintaining a constant drain current due to process variations, leading to significant changes in drain current and gain characteristics, especially when operating with a single positive power source and limited withstand voltage, making it difficult to reduce current consumption and ensure stable operation in milliwave band applications.
Innovation Solution
A current reuse type FET amplifier is designed with additional transistors, resistances, and diodes to independently control the gate voltages of FETs, allowing for adjustments based on process variations, thereby reducing drain current and voltage variations, and ensuring operation within the FET's withstand voltage range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a current reuse type circuit configuration is used to reduce power consumption, then current consumption is reduced, but drain current varies significantly due to process variations
Solution Approach 1:
The patent adjusts the gate voltage of the FET to compensate for process variations. By changing the gate voltage parameter, the drain current is stabilized despite variations in transistor characteristics due to manufacturing process differences, thereby maintaining reliable operation while using the current reuse configuration.
2Reliability
If additional transistors and control circuits are added to stabilize drain current, then drain current stability is improved, but device complexity increases
Solution Approach 1:
The patent employs a feedback mechanism where the drain current is monitored and the gate voltage is adjusted accordingly to maintain stable operation. This feedback approach stabilizes the drain current without requiring complex additional circuitry, as the control leverages existing circuit elements and their interrelationships.
3Reliability
If gate voltage is adjusted to compensate for process variations, then drain current stability is improved, but control complexity increases
Solution Approach 1:
The patent implements a self-adjusting bias control mechanism where the circuit automatically compensates for process variations through inherent feedback relationships. The gate voltage adjustment is performed autonomously based on the operating conditions, eliminating the need for external manual calibration or complex control systems.
Data Source
AI summary
A current reuse type FET amplifier according to the present invention has a capacitance provided between a drain of a first FET in a first stage and a gate of a second FET in a next stage, electrically separates a gate voltage of the second FET from a drain voltage of the first FET, and includes a control circuit controlling the gate voltage of the first FET and the gate voltage of the second FET so that a variation of a drain current of the second FET and a variation of a drain voltage of the first FET are reduced in accordance with a variation of a saturation current Idss of the FET. Furthermore, the current reuse type FET amplifier according to the present invention uses only a depression mode FET to provide a circuit configuration operable with a positive single power source.