RF Amplifier Bias Circuit Using Schottky Diode at Low Voltage
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Solution Overview
Problem
Transistors made of compound semiconductors do not operate effectively at low power supply voltages due to their higher threshold voltage compared to elemental semiconductors, leading to a decrease in output power during large signal conditions.
Innovation Solution
A radio frequency amplification circuit is designed using a compound semiconductor amplification transistor, a compound semiconductor biasing transistor, and a Schottky barrier diode, where the threshold voltage of the Schottky barrier diode is lower than that of the biasing transistor, allowing for bias supply to the amplification transistor even at low voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a transistor made of compound semiconductor is used to achieve higher output in high frequency band, then the output power is improved, but the transistor cannot operate at low power supply voltage due to higher threshold voltage
Solution Approach 1:
A Schottky barrier diode is introduced as an intermediary component between the power supply and the compound semiconductor transistor. The diode has a lower threshold voltage than the transistor, allowing it to conduct at low voltages and provide a bias current that keeps the transistor in active region even when the power supply voltage is low, thus enabling the transistor to operate reliably at low voltages while maintaining high frequency output capability
Solution Approach 2:
The invention changes the voltage parameter by using a Schottky barrier diode with a specifically lower threshold voltage compared to the compound semiconductor transistor. This parameter difference allows the diode to activate first at low voltages and provide the necessary bias, effectively solving the low-voltage operation problem without compromising the high-frequency output performance
2Device complexity
If bias supply circuit is simplified, then device complexity is reduced, but gain decreases at low input signal power and low voltage
Solution Approach 1:
The Schottky barrier diode automatically activates based on the power supply voltage level. When the voltage is low, the diode conducts and provides the necessary bias current to maintain gain. When voltage is sufficient, the diode naturally stops conducting as the transistor's own bias requirements are met. This self-regulating mechanism maintains high gain at low power without requiring complex control circuits
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 circuit effectively increases gain at low input signal powers and low voltages, while maintaining sufficient bias supply to the amplification transistor, thus enhancing the overall performance of the RF amplification circuit.
Implementation Method 1
a Schottky barrier diode having an anode electrically coupled to the base of the first transistor and a cathode electrically coupled to the emitter of the first transistor. A threshold voltage of the Schottky barrier diode is lower than a threshold voltage of the first transistor.
Data Source
AI summary
A radio frequency amplification circuit includes an amplification transistor, a first transistor, and a Schottky barrier diode. The amplification transistor has a base to which a radio frequency signal is supplied and a collector from which the radio frequency signal amplified is outputted, and is made of a compound semiconductor. The first transistor has a base to which a first bias is supplied, and an emitter electrically coupled to the base of the amplification transistor and configured to supply a second bias to the base of the amplification transistor, and is made of the compound semiconductor. The Schottky barrier diode has an anode electrically coupled to the base of the first transistor and a cathode electrically coupled to the emitter of the first transistor.