Photodiode Current Integrator With Feedback Multiplication
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Solution Overview
Problem
Existing photodiode current integrator circuits face limitations in integration speed due to the requirement for small integration capacitor values and specific switch parameters, which narrows the choice of applicable switches and limits integration speed.
Innovation Solution
A single-stage active integrator with multiplication of photodiode current, utilizing a first and second feedback resistor connected along feedback paths of an operational amplifier, an integration capacitor connected to common ground, and a reset switch, allowing for a larger integration capacitor value and reduced leakage current requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a small integration capacitor value is used for fast integration times, then integration speed is improved, but the switch must have very low leakage currents and low internal capacitances which limits switch selection
Solution Approach 1:
The patent changes the electrical parameters of the circuit by introducing a multiplication factor through the feedback resistor ratio (R1/R2). This allows the integration capacitor value to be increased while maintaining the same effective integration speed, as the multiplied current compensates for the larger capacitor value. Consequently, switches with higher leakage currents and larger internal capacitances become acceptable, expanding the range of usable switches.
2Speed
If a small integration capacitor value is used, then integration speed is improved, but leakage current requirements become much more stringent
Solution Approach 1:
The circuit modifies the current parameter by multiplying the photodiode current through the feedback resistor network. This current multiplication allows the use of larger integration capacitors that are less sensitive to leakage currents, thereby relaxing the leakage current requirements while maintaining integration performance.
3Speed
If a small integration capacitor value is used, then integration speed is improved, but the circuit becomes more sensitive to noise
Solution Approach 1:
By multiplying the photodiode current before integration, the circuit can use larger integration capacitor values. Larger capacitors have higher impedance at low frequencies, which provides better noise rejection and reduces the circuit's sensitivity to noise while maintaining fast integration capabilities through the current multiplication effect.
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
Enables higher integration capacitor values while maintaining low leakage currents, increasing integration speed and flexibility in switch selection, and reducing noise penetration.
Implementation Method 1
a first feedback resistor connected along a negative feedback path of an operational amplifier between an output of the operational amplifier and a negative input of the operational amplifier. The photodiode current integrator also includes a second feedback resistor connected along a positive feedback path of the operational amplifier
Implementation Method 2
a photodiode connected to the positive input of the operational amplifier and connected to the negative input of the operational amplifier
Implementation Method 3
the integration capacitor connected to the positive input of the operational amplifier and connected to a common circuit ground
Data Source
AI summary
An embodiment of this disclosure provides an automated payment apparatus. The apparatus includes a photodiode current integrator configured to charge an integration capacitor. The photodiode current integrator includes a first feedback resistor connected along a negative feedback path of an operational amplifier between an output of the operational amplifier and a negative input of the operational amplifier. The photodiode current integrator also includes a second feedback resistor connected along a positive feedback path of the operational amplifier between the output of the operational amplifier and a positive input of the operational amplifier. The photodiode current integrator also includes an integration capacitor connected to the positive input of the operational amplifier and to common circuit ground. The photodiode current integrator also includes a reset switch connected to the positive input of the operational amplifier and to common circuit ground or to additional voltage source. The photodiode current integrator also includes a photodiode connected to the positive input and the negative input of the operational amplifier.