Open-Loop Bias Circuit for Temperature-Stable Stacked Amplifiers
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Solution Overview
Problem
Existing bias circuits for stacked device amplifiers are either temperature-dependent and unstable or limit current and efficiency due to closed-loop feedback, lacking performance independence from process and temperature variations.
Innovation Solution
An open-loop bias circuit design using a voltage divider module with temperature-dependent resistive cells and a voltage buffer module to generate temperature-independent control voltages, evenly distributing the power supply across stacked devices, ensuring stability and adjustable current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If simple resistive divider biasing networks are used, then the bias circuit is inherently stable and simple, but the performance is dependent on process and temperature variation
Solution Approach 1:
The patent changes the parameters of the bias circuit by introducing temperature-dependent resistors with specific temperature coefficients. These resistors are designed to have opposite temperature dependencies that cancel each other out, making the overall bias voltage independent of temperature and process variations while maintaining open-loop simplicity
Solution Approach 2:
The patent creates a composite bias network by combining resistors with different temperature coefficients in a specific configuration. The composite structure integrates a temperature-independent reference voltage source with temperature-dependent dividers, achieving both stability and environmental independence
2Reliability
If closed loop bias circuits with feedback are used, then temperature stability and voltage regulation are provided, but the bias networks can be potentially unstable and current is limited at fixed bias
Solution Approach 1:
The patent extracts the feedback mechanism from the bias circuit, removing the closed-loop structure entirely. By taking out the feedback element, the circuit becomes an open-loop system that is inherently stable and does not suffer from feedback-induced oscillations or instability, while still achieving temperature independence through carefully selected resistor combinations
Solution Approach 2:
The bias circuit serves itself by using intrinsic properties of the resistors (temperature coefficients) to automatically compensate for temperature variations without requiring external feedback control. The circuit self-regulates its bias voltage to remain stable across temperature ranges
3Reliability
If closed loop feedback is used, then voltage regulation is achieved, but the current of the amplifier is limited at fixed bias, thereby limiting output power and efficiency
Solution Approach 1:
The patent makes the bias circuit dynamic by allowing the bias voltage to adapt to different operating conditions through the temperature-dependent resistor network. This dynamic behavior enables the circuit to maintain proper voltage distribution across stacked devices while allowing the amplifier to operate at higher currents and power levels without being constrained by fixed feedback limits
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 bias circuit provides stable, temperature-independent performance with even power distribution across stacked devices, enhancing output power and efficiency by allowing variable current draw.
Implementation Method 1
generating, by the voltage divider bias module from a power supply voltage (VDD), a plurality of control voltage biases, which comprise a plurality of voltage references plus an offset voltage term (Vtemp). In one or more embodiments, the plurality of voltage references are each proportional to a division of the power supply voltage (VDD)
Implementation Method 2
the offset voltage term (Vtemp) is proportional to temperature and is a function of process variation. In one or more embodiments, the voltage divider bias module comprises a plurality of temperature-dependent resistive cells connected together in series
Data Source
AI summary
An open loop process and temperature independent bias circuit for stacked device amplifiers is disclosed herein. In one or more embodiments, a method for biasing a stacked high-voltage signal amplifier with a voltage divider bias module comprises generating, by the voltage divider bias module from a power supply voltage (VDD), a plurality of control voltage biases, which comprise a plurality of voltage references plus an offset voltage term (Vtemp). In one or more embodiments, the plurality of voltage references are each proportional to a division of the power supply voltage (VDD), and the offset voltage term (Vtemp) is proportional to temperature and is a function of process variation. The method further comprises biasing, a plurality of devices of the stacked high-voltage signal amplifier, with the control voltage biases.