Differential Amplifier Circuit With Independent Output Voltage Range
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Solution Overview
Problem
Differential amplifier circuits struggle to release an output voltage independently of the voltage range of a differential input voltage, requiring complex configurations with multiple op-amps and resistor elements.
Innovation Solution
A differential amplifier circuit comprising NMOS or PMOS transistors, constant current sources, and an op-amp, with a voltage/current converting section and a current/voltage converting section operating at independent supply voltages, allowing the output voltage to be set independently of the differential input voltage range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple op-amps and resistor elements are used to achieve independent output voltage, then the output voltage independence is improved, but the device complexity increases
Solution Approach 1:
The circuit is divided into two independent sections: a first section with a first op-amp for processing differential input voltage, and a second section with a second op-amp for processing reference voltage. Each section operates independently with its own operational amplifier and resistor elements, allowing the output voltage to be independently controlled without requiring a single complex integrated circuit.
2Device complexity
If a simple circuit configuration is used, then the device complexity is reduced, but the ability to release output voltage independently deteriorates
Solution Approach 1:
The circuit is divided into two independent sections: a first section with a first op-amp for processing differential input voltage, and a second section with a second op-amp for processing reference voltage. Each section operates independently with its own operational amplifier and resistor elements, allowing the output voltage to be independently controlled without requiring a single complex integrated circuit.
3Ease of operation
If input terminals are connected to voltage followers, then the input impedance is improved, but the device complexity increases
Solution Approach 1:
The first and second operational amplifiers serve multiple functions: they provide high input impedance through voltage follower configuration while simultaneously enabling independent voltage processing and output control. This multi-functionality eliminates the need for additional dedicated impedance-matching components.
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 achieves a simple configuration capable of releasing an output signal within a voltage range independent of the differential input signal, with high impedance at input terminals and efficient operation across varying input voltage conditions.
Implementation Method 1
a voltage/current converting section that operates at a first supply voltage to convert a differential voltage of a differential input voltage into a current according to the differential voltage
Implementation Method 2
a current/voltage converting section that operates at a second supply voltage independent of the first supply voltage to convert a current output from the voltage/current converting section into a voltage according to the current
Data Source
AI summary
A differential amplifier circuit of simple circuit configuration is disclosed, which is capable of releasing an output signal within a voltage range independent of the voltage range of a differential input signal. The differential amplifier circuit 1 includes: NMOS transistors N1, N2 that constitute a first differential pair configured to input a differential input voltage; a resistor element Ra connected to drain terminals X1, X2 of the NMOS transistors N1, N2; an op-amp OP having input terminals connected to the drain terminals X1, X2; and NMOS transistors N3, N4 that constitute a second differential pair configured to input an output voltage of the op-amp OP and a reference voltage. The drain terminals of the first differential pair are connected to drain terminals, respectively, of the second differential pair.