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26 Jun 2015


by Ron Quan:

In some JFET op amps such as the AD743, the input capacitance is in the order of 18 to 20 pF. In comparison, with an LSK489 dual FET, the input capacitance is in the order of 3 pF, which will be suitable for low noise photodiode applications. In this section we will see why it is important to have low equivalent input noise and low input capacitance in a photodiode preamp.

A Guide to using FETS for Sensor Applications – [Link]

30 Jan 2015


The OPT3001 is a sensor that measures the intensity of visible light. The spectral response of the sensor tightly matches the photopic response of the human eye and includes significant infrared rejection.

The OPT3001 is a single-chip lux meter, measuring the intensity of light as visible by the human eye. The precision spectral response and strong IR rejection of the device enables the OPT3001 to accurately meter the intensity of light as seen by the human eye regardless of light source. The strong IR rejection also aids in maintaining high accuracy when industrial design calls for mounting the sensor under dark glass for aesthetics. The OPT3001 is designed for systems that create light-based experiences for humans, and an ideal preferred replacement for photodiodes, photoresistors, or other ambient light sensors with less human eye matching and IR rejection.

OPT3001 – Ambient Light Sensor – [Link]

19 Jan 2015


Vishay Intertechnology is broadening its optoelectronics portfolio with the introduction of two new automotive-grade high-speed silicon PIN photodiodes in top-view, surface-mount packages measuring 5 mm by 4 mm by 0.9 mm. Offering a large sensitive area of 7.5 mm2, the Vishay Semiconductors VEMD5010X01 and VEMD5110X01 provide high radiant sensitivity with a reverse light current of 48 µA and a very low dark current of 2 nA for automotive, industrial, and medical applications.

The AEC-Q101-qualified devices are manufactured using Vishay’s new foil assisted mold (FAM) technology. The photodiodes’ leadframe, bond wire, and connection pads are molded in a black epoxy, while a free cavity above the radiant sensitive area allows light to enter the package for signal generation. This design enables a smaller overall package size with a lower height profile, while maintaining a large radiant sensitive area. In addition, thermal stress on the bond is reduced for increased robustness and reliability.

Vishay Intertechnology Automotive-Grade PIN Photodiodes Deliver 7.5 mm² Sensitive Area in Low-Profile Packages – [Link]

26 Nov 2014


Smoke detector is a device incorporated on fire alarm system; it is usually installed on buildings to alarm the occupants when there is a fire (when there’s smoke, there’s fire). This provides the crucial early warning to escape injury or death in fire. This project uses optical method design; the sensing part is the photo chamber that is composed of infrared light source and a photoelectric receiver (photodiode).

The design of this project is not so complicated because of the specialized IC (Integrated Circuit) intended for smoke detection. The RE46C190 smoke detector IC provides all the required features for a photoelectric smoke detector type of electronic project with minimal external component needed. During standby mode, the RE46C190 IC is programed to check the battery condition every 86 seconds and the chamber integrity every 43 seconds. Interconnection between multiple detectors (through I/O PIN-12) is also possible; this will activate all the connected detectors when one of the units is triggered.

The 1µF capacitor should be located as close as possible to the device power pins, and 10µF capacitor should be located as close as possible to VSS. Schottky diode must have a maximum peak current rating of at least 1.5A. For best results, it should have a forward voltage specification of less than 0.5V at 1A and low reverse leakage. Also, the 10mH inductor must have a maximum peak current rating of at least 1.5A. With the IC’s very low power consumption, this project only requires a three-volt DC power supply (simply use a 3 volt battery).

Photoelectric Smoke Detector – [Link]

20 Oct 2014


An app note on Gamma-photon radiation detector (PDF) by Maxim:

A PIN photodiode, four low-noise op amps and a comparator are used to detect individual photons of gamma radiation. The schematic, design considerations and component selection are discussed.


Gamma-photon radiation detector – [Link]

4 Oct 2014


by elektor.com:

The single LTC6268 and dual LTC6269 FET-input op amps from Linear Technology feature a tiny (3 fA typical) input bias current at 25°C (peaking at 4 pA max over the entire –40°C to 125°C temperature range). Their input characteristics make them a good match for photodiode, photomultiplier and other applications using high impedance, high speed sensors. The low distortion output signal can be used by an A/D converter. A shutdown feature lowers power consumption when an amplifier is not in use.

High Speed Trans-impedance Amp – [Link]

17 Sep 2014


by Martin Jagelka , Martin Daricek & Martin Donoval :

Continuous monitoring of heart activity permits measurement of heart rate variability (HRV), a basic parameter of heart health and other diseases.

This Design Idea is a new design of pulse oximetry that excels in its simplicity and functionality. Due to its capabilities, it can be used as a standalone device, able to monitor heart rate and oxygen saturation.

The core of the system is composed of the ultra-bright red LED (KA-3528SURC), infrared LED (VSMB3940X01-GS08), and a photodiode (VBP104SR) sensitive to both wavelengths of light at the same level.

Simple pulse oximetry for wearable monitor – [Link]

19 Jul 2014


by JamecoElectronics @ instructables.com:

Build a DIY geiger counter that uses a PIN photodiode as a substitute for an expensive Geiger-Mueller tube. It detects alpha and beta radiation particles. The circuit is soldered onto a small protoboard and everything is placed in an aluminum enclosure. Copper tubing and a piece of aluminum foil is used to help filter out noise and RF interference.

Pocket Photodiode Geiger Counter – [Link]

18 Jun 2014

This Photodiode based Alarm can be used to give a warning alarm when someone passes through a protected area. The circuit is kept standby through a laser beam or IR beam focused on to the Photodiode. When the beam path breaks, alarm will be triggered. The circuit uses a PN Photodiode in the reverse bias mode to detect light intensity. In the presence of Laser / IR rays, the Photodiode conducts and provides base bias to T1.

The NPN transistor T1 conducts and takes the reset pin 4 of IC1 to ground potential. IC1 is wired as an Astable oscillator using the components R3, VR1 and C3. The Astable operates only when its reset pin becomes high. When the Laser / IR beam breaks, current through the Photodiode ceases and T1 turns off. The collector voltage of T1 then goes high and enables IC1. The output pulses from IC1 drives the speaker and alarm tone will be generated.

A simple IR transmitter circuit is given which uses Continuous IR rays. The transmitter can emit IR rays up to 5 meters if the IR LEDs are enclosed in black tubes.

555 Photodiode alarm – [Link]

8 Jun 2014


by Ashok Bindra:

Whether it is used for biasing avalanche photodiodes (APDs) found in optical receivers, driving photoflash tubes in flash cameras, or charging high-voltage capacitors, the need for high-voltage sources continues to grow. Consequently, in battery-powered units where the input supply voltage is low, step-up or boost DC/DC converters are required to generate voltages that can be several times the input. To address these requirements, suppliers such as Analog Devices, Linear Technology, Maxim Integrated, and Micrel Inc., among others, have produced boost converters with output voltages at 70 V and above.

This article examines such solutions and discusses the topologies and techniques used by each to boost output voltages by ratios of 10:1 or better in order to generate high-DC voltages from very-low DC inputs.

DC/DC Converter Topologies and Techniques to Obtain High Boost Ratios – [Link]





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