Transimpedance Amplifier Circuit for Low-Voltage Wide Output Swing
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Solution Overview
Problem
Light receiving circuits face challenges in maintaining a broad frequency bandwidth while minimizing electrical power consumption, particularly when using MOS transistors at low voltage supplies, as the output voltage range narrows when the MOS transistor of the output stage is drain grounded.
Innovation Solution
A transimpedance amplifier design incorporating a first and second MOS transistor with a current mirror circuit and a feedback resistor, where both transistors are source grounded, allowing for a broader output voltage range and efficient low-voltage operation by optimizing the resistance value and current ratios, enabling wider frequency amplification up to 100 MHz.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a MOS transistor of the output stage is drain grounded, then low voltage and low current operation is achieved, but the output voltage range narrows
Solution Approach 1:
The patent inverts the conventional drain-grounded configuration by grounding the source instead. This inversion allows the output voltage to swing from ground to near the power supply voltage, maximizing the output voltage range while maintaining low power consumption through source grounding.
Solution Approach 2:
The patent changes the grounding parameter from drain to source, fundamentally altering the operating point and voltage swing characteristics of the MOS transistor. This parameter change enables simultaneous achievement of low power consumption and broad output voltage range.
2Power
If a MOS transistor is used in the transimpedance amplifier, then low voltage and low current operation is enabled, but the output voltage range is limited at low power supply voltage
Solution Approach 1:
The patent applies source grounding instead of drain grounding in the MOS transistor output stage, inverting the conventional configuration. This enables the output voltage to utilize the full power supply range while maintaining low operating voltage and current levels suitable for low-power applications.
Solution Approach 2:
The source-grounded MOS transistor configuration provides multi-functionality by simultaneously achieving low voltage operation, low current consumption, and broad output voltage range, making it universally applicable to low-power optical communication systems.
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 design achieves a broader output voltage range and higher frequency amplification, effectively addressing the power consumption and voltage range limitations, making it suitable for low-voltage applications like optical sensors and couplers.
Implementation Method 1
a photodiode or a phototransistor or the like, and the amplifier is a transimpedance amplifier that is capable of amplifying photoelectric current
Data Source
AI summary
A transimpedance amplifier includes a first MOS transistor, a current mirror circuit, a second MOS transistor, a load and a first feed back resistor. The first MOS transistor has a gate terminal to which a photodiode is connected. An output current of the first MOS transistor is input to the current mirror. The second MOS transistor has a gate terminal to which a voltage of an output terminal of the current mirror circuit is input. A source of the second MOS transistor is grounded. A polarity of the second MOS transistor is same as a polarity of the first MOS transistor. A first feedback resistor is connected between the gate terminal of the first MOS transistor and a drain terminal of the second MOS transistor. The second MOS transistor outputs a voltage corresponding to the voltage of the output terminal from the drain terminal.