The current-voltage characteristics of a photodiode under illumination are also similar. Phototransistor is used as solid state switch unlike photodiode. But do you know how does it work? Photodiodes are much faster than phototransistors (nanoseconds vs. microseconds) Gain Phototransistors have a higher gain. Optocoupler Optocouplers are used in electronics-sensitive applications. The phototransistor is widely used in electronics devices likes smoke detectors, infrared receiver, CD players, lasers etc.
Photodiodes may contain optical filters, built-in lenses, and may have large or small surface areas.Photodiodes usually have a slower response time as their surface area increases. It's used by placing it reverse-biased with a series resistor to measure the leakage current through the diode. Dark current of phototransistor is much higher than photodiode. The light detector can be any one of a number of different types of device from a photodiode to a phototransistor, photodarlington, etc. A p-n junction photodiode can be operated under photovoltaic conditions similar to that of a solar cell. But there are few major differences, such as: 1. Temperature Response Photodiodes vary less with temperature Applications. A phototransistor is more efficient as compared to a photodiode. We all work with LED in almost every electronics project, whether it is used for giving a good look or a to give some sort of signal. Thus, it is termed as Light-emitting diode.On the contrary, photodiode generates current when it is exposed to the source of light. The photodiode and phototransistor both convert the light energy into the electrical energy. Photodiode Vs Phototransistor. The major difference between diode and photodiode is that a diode is a semiconductor device which conducts when it is forward biased while the photodiode conducts in reversed biased mode. The LED operates on the principle of electro-luminance while photodiode works on the principle of the photoconduction. Photodiodes require an amplifier to use. A photo-diode is a diode who's leakage current gradually increases with the amount of IR that hits it. A photodiode consists of a semiconductor diode, that generates current when exposed to light. The main differences between Photodiode and Phototransistor are explained here. The light emitter and detector are tailored to match one another, having matching wavelengths so that the maximum coupling is achieved. Optocoupler Optocouplers are used in electronics-sensitive applications. Re: Photoresistors vs Phototransistors vs Photodiodes!

A photodiode is "A semiconductor diode which generates a potential difference or changes its electrical resistance when illuminated. « Reply #12 on: March 22, 2009, 01:43:08 PM » It has nothing to do with precision when using an ADC - only when using a single point to shift between light or not. Phototransistors vs. Photodiodes Before getting into phototransistors, it helps to understand how they are different from photodiodes. Photodiodes are much faster than phototransistors (nanoseconds vs. microseconds) Gain Phototransistors have a higher gain. The advantage of the phototransistor is that you get the gain of the transistor, so you get more output response for the same input IR level, as compared to the PIN photodiode. A photodiode is a semiconductor device that converts light into an electrical current.The current is generated when photons are absorbed in the photodiode. The important applications of phototransistor are IR receiver, position sensing. Difference Between Photodiode & Phototransistor One of the major difference between the photodiode and the phototransistor is that the photodiode uses PN-junction diode which converts the light energy into an electric current, whereas the phototransistor uses the ordinary transistor (NPN transistor) for the conversion of light into current.

The important applications of photodiode are light detecting sensor, smoke detector. The conduction in the diode is possible due to the voltage applied externally, while the conduction in the photodiode is possible only when it is illuminated by the light source.