Open-Loop Transimpedance Amplifier for Fast Infrared Diode Sensing
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Solution Overview
Problem
Traditional infrared receiver circuits for learning remote control devices are expensive and power-consuming due to their integration with discrete components outside the microcontroller integrated circuit, leading to increased die area and slow response times caused by high input impedance.
Innovation Solution
A novel open-loop transimpedance amplifier (OLTA) is integrated into the microcontroller, featuring a diode-connected N-channel transistor circuit with low input impedance, minimizing parasitic capacitance and consuming less than 30 microamperes of current, allowing for efficient and fast infrared signal detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional infrared receiver circuits are integrated with discrete components outside the microcontroller, then sensitivity is improved, but power consumption increases and die area increases
Solution Approach 1:
The patent merges the infrared receiver circuit with the microcontroller integrated circuit, integrating the photodiode and amplifier directly onto the same die. This eliminates the need for discrete external components while maintaining detection sensitivity, thereby reducing power consumption and die area compared to traditional discrete implementations.
Solution Approach 2:
The patent employs a novel open-loop transimpedance amplifier design with modified operating parameters that achieves adequate sensitivity for remote control applications without requiring the high sensitivity of conventional photocurrent amplifiers. This parameter optimization allows integration while consuming less than 30 microamperes of current.
2Measurement precision
If traditional operational amplifier circuits are used, then sensitivity is improved, but response time increases due to high input impedance
Solution Approach 1:
Instead of using high input impedance amplifiers that provide high sensitivity but slow response, the patent inverts the approach by using low input impedance amplifiers with transimpedance gain. This achieves adequate sensitivity through the transimpedance conversion rather than high impedance, thereby enabling fast response times suitable for remote control signal detection.
Solution Approach 2:
The patent changes the amplifier design parameters from conventional high-impedance photocurrent amplifiers to open-loop transimpedance amplifiers with low input impedance. This parameter change fundamentally alters the operating characteristics to achieve both adequate sensitivity and fast response times.
3Reliability
If discrete components are used outside the microcontroller, then performance is improved, but device complexity and cost increase
Solution Approach 1:
The patent combines the infrared receiver circuit and microcontroller into a single integrated device, eliminating the need for separate discrete components. This merging reduces device complexity and assembly requirements while maintaining the performance needed for remote control learning and emulation functions.
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 OLTA solution reduces power consumption and response time, enabling a compact and cost-effective fully integrated infrared receiver circuit within the microcontroller, suitable for learning remote control devices with improved performance and reduced die area.
Implementation Method 1
A photodiode is coupled to an input terminal of the open-loop transimpedance amplifier (OLTA)
Data Source
AI summary
A microcontroller integrated circuit includes an open-loop transimpedance amplifier (OLTA). An input lead of the OLTA is a terminal of the microcontroller. The cathode of a photodiode is connected to VDD and the anode is connected to the terminal. The OLTA maintains the photodiode in a strongly reverse-biased condition, thereby keeping diode capacitance low and facilitating rapid circuit response. The input of the OLTA involves a diode-connected field effect transistor that provides a low impedance. This low impedance decreases as the diode current increases, thus providing effective clamping of the voltage on the terminal. By this clamping, the amount of photodiode capacitance discharging necessary when transitioning from a high input current condition to a low input current condition is reduced, thereby further improving amplifier response time. The OLTA is small and consumes less than thirty microamperes and functions to mirror photodiode current and compare to a predetermined level.