Bias Circuitry Stabilizing PHEMT Amplifier Current
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Solution Overview
Problem
Pseudomorphic high electron mobility transistor (PHEMT) technology experiences unsatisfactorily large amplifier current and gain variations in both enhancement and depletion modes, which existing solutions have not adequately addressed, particularly in high yield production and low-noise amplifier operations.
Innovation Solution
The implementation of circuitry with a reference current generator and a reference current governor, utilizing field effect transistors (FETs) to maintain a steady reference current and correct total current flowing through the circuitry, thereby stabilizing amplifier bias current, including a depletion mode current governor to address variations in both enhancement and depletion modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If enhanced epitaxial processes and process variation limits are used to control threshold voltage, then manufacturing precision improves, but device complexity and production cost increase without yielding widely accepted improvements
Solution Approach 1:
The patent introduces a reference current governor circuit as an intermediary component that actively compensates for threshold voltage variations. This circuit includes a reference current generator and governor circuitry that senses and corrects current variations caused by process deltas, thereby achieving stable amplifier operation without relying on complex epitaxial process control
Solution Approach 2:
The reference current governor implements a feedback mechanism where the governor current is adjusted based on the actual reference current flowing through the FETs. This closed-loop control automatically compensates for threshold voltage drift and process variations, replacing the need for complex open-loop process control methods
2Stability of the object's composition
If transistor bias techniques are applied to reduce current variations, then amplifier current stability improves, but supply voltage sensitivity increases
Solution Approach 1:
The patent changes the operating parameters of the bias circuit by using depletion mode FETs with specific W/L ratios and configuring the reference current governor to operate at optimized current levels. This allows the circuit to achieve current stability while maintaining reduced sensitivity to supply voltage variations through proper parameter selection
3Stability of the object's composition
If amplifier circuit topologies are modified to reduce gain variations, then amplifier gain stability improves, but suitability for low-noise amplifier operation deteriorates
Solution Approach 1:
The patent segments the bias control function into separate components: a reference current generator for establishing the baseline current, and a reference current governor for correcting variations. This segmentation allows independent optimization of each function to achieve both gain stability and low-noise performance without compromising either aspect
Data Source
AI summary
Circuitry having a reference current generator and a reference current governor is disclosed. The reference current governor includes field effect transistors (FETs) that are sized such that a governor current governs a reference current flowing through the first FET to maintain the reference current within a desired reference current range.