Power Amplifier Bias Circuit Using a Gate-Open FET Resistor
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Solution Overview
Problem
Bi-FET power amplifiers face challenges in suppressing leakage current without increasing chip areas and manufacturing costs, particularly due to the requirement for high resistance values that are difficult to achieve with thin metal film resistors.
Innovation Solution
The use of a gate open long-channel FET resistor in the power amplifier, which allows for high resistance values to be realized without adding process steps, thereby reducing chip area and manufacturing costs while effectively suppressing leakage current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If thin metal film resistors are used to achieve high resistance values, then leakage current suppression is improved, but chip area and manufacturing costs increase
Solution Approach 1:
The patent changes the parameter of resistance value by using a long-channel FET resistor instead of a thin metal film resistor. The long-channel FET provides high resistance (100 kΩ or more) through its inherent channel resistance characteristics, eliminating the need for large-area thin metal film resistors while maintaining effective leakage current suppression.
Solution Approach 2:
The patent uses the FET resistor structure that is already present in the Bi-FET process fabrication, copying the existing device geometry and electrical characteristics to serve as a high-value resistor. This approach leverages the available process technology without requiring additional specialized resistor fabrication steps.
2Object-affected harmful factors
If thin metal film resistors are used to achieve high resistance values, then leakage current suppression is improved, but manufacturing costs increase
Solution Approach 1:
The long-channel FET serves multiple functions: it acts as both an enable switch and a high-value resistor (100 kΩ or more) for leakage current suppression. This multi-functionality eliminates the need for separate thin metal film resistors, reducing manufacturing complexity and cost while maintaining effective leakage suppression.
Solution Approach 2:
The patent changes the resistance implementation from thin metal film to long-channel FET, utilizing the FET's channel resistance characteristics. This parameter change allows high resistance values to be achieved through device geometry (long channel length) rather than through expensive thin metal film deposition processes.
3Use of energy by moving object
If enable voltage is reduced, then power consumption is improved, but leakage current control becomes more difficult
Solution Approach 1:
The patent implements feedback control through the enable circuit that monitors and adjusts the operating state of the FET resistor. The enable voltage controls the FET's operating point, and the circuit is designed to maintain proper leakage suppression across the enable voltage range, ensuring stable performance even at reduced voltage levels.
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 solution effectively suppresses leakage current to several microamperes or less at a wide range of enable voltages without increasing chip area or manufacturing costs, achieving improved performance and cost efficiency.
Implementation Method 1
a FET resistor connected between the first electrode of the transistor and the power source terminal, wherein a gate electrode of the FET resistor is open
Data Source
AI summary
A power amplifier comprises: an amplifying transistor for amplifying an input signal; a reference voltage generating circuit which generates a reference voltage; a bias circuit generating a bias voltage based on the reference voltage and supplying the bias voltage to the amplifying transistor; and a booster elevating an enable voltage input from outside and outputting the enable voltage. The reference voltage generating circuit is turned ON/OFF in correspondence with an output voltage of the booster. The booster includes: an enable terminal to which the enable voltage is applied; a power source terminal connected to a power source; a transistor having a control electrode connected to the enable terminal, a first electrode connected to the power source terminal, and a second electrode that is grounded; and a FET resistor connected between the first electrode of the transistor and the power source terminal. A gate electrode of the FET resistor is open.