Current-to-Voltage Conversion Circuit With Feedback Noise Suppression
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Solution Overview
Problem
Existing circuits, such as those for capacitor microphones, require many external components and are difficult to apply to other elements like sensors, leading to significant noise superimposition due to power supply and transmission line noise.
Innovation Solution
A conversion circuit that converts input current into output voltage, utilizing a regulator to detect voltage differences and adjust current flow to maintain a reference voltage, with configurations involving various transistors and resistors to reduce noise, including operational amplifiers and field effect transistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a capacitor microphone is powered using a resistor connected to the power supply voltage, then the microphone can operate, but power supply noise is superimposed on the output signal
Solution Approach 1:
The patent introduces a regulator circuit as an intermediary between the power supply voltage and the capacitor microphone. This regulator acts as a mediator that provides a stable reference voltage to the microphone, preventing power supply noise from being superimposed on the output signal while still enabling the microphone to operate properly.
Solution Approach 2:
The regulator circuit employs feedback control to maintain a stable reference voltage. By continuously monitoring the voltage at the first terminal and adjusting the current flow accordingly, the circuit ensures that the reference voltage remains constant despite fluctuations in the power supply voltage, thereby eliminating noise superimposition.
2Object-affected harmful factors
If a noise cancellation circuit is added to cancel power supply noise, then noise superimposition is reduced, but the circuit requires many external components and is difficult to apply to other elements
Solution Approach 1:
The regulator circuit is designed with universal applicability, using standard components (operational amplifier, transistors, resistors) that can be applied to various sensing elements beyond capacitor microphones, including piezoelectric sensors, pressure sensors, acceleration sensors, and crystal oscillators. This multi-functional design reduces the need for element-specific external components.
Solution Approach 2:
The patent combines multiple functions into a single integrated circuit block. The regulator circuit simultaneously provides noise cancellation, stable voltage reference, and current control functions, eliminating the need for separate external noise cancellation components and reducing overall circuit complexity.
3Reliability
If the sensor and amplifier circuit are installed apart from each other, then the amplifier can use a stable power supply, but external noise is superimposed on the signal
Solution Approach 1:
The regulator circuit serves as an intermediary between the power supply and the sensor, providing a stable reference voltage that isolates the sensor from power supply noise. This allows the sensor to be positioned close to the amplifier without introducing noise, as the regulator effectively blocks noise transmission through the power supply line.
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 proposed circuit significantly reduces noise superposition, allowing for robust operation against external noise and enabling recording and reproduction of low-level signals without being buried in noise.
Implementation Method 1
a regulator configured to detect a difference between a voltage at the first terminal and a predetermined reference voltage, and, when the voltage at the first terminal is higher than the reference voltage, perform control of adjusting an amount of current flowing from the third terminal to the second terminal according to a magnitude of the difference, and maintaining the voltage at the first terminal at the reference voltage
Data Source
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AI summary
A conversion circuit is a conversion circuit that converts an input current into an output voltage, the conversion circuit including a first terminal that is an input unit for the input current; a second terminal that is ground, a third terminal that is an output unit for an output voltage, the third terminal being configured to supply a power supply voltage via a power supply resistor, a first resistor, one end of which is connected to the first terminal and the other end of which is connected to the third terminal, and a regulator configured to detect a difference between a voltage at the first terminal and a predetermined reference voltage, and, when the voltage at the first terminal is higher than the reference voltage, perform control of adjusting an amount of current flowing from the third terminal to the second terminal according to a magnitude of the difference, lowering a voltage of the third terminal, and maintaining the voltage at the first terminal at the reference voltage, in which a gain of the conversion circuit is determined by the first resistor.