A phototransistor is "A junction transistor which responds to incident light by generating and amplifying an electric current. "A photodiode is "A semiconductor diode which generates a potential difference or changes its electrical resistance when illuminated. "Now here are some more expanded explanations. A phototransistor is a photosensible semiconductor device comprising three electrodes. Light or ultraviolet light activates this bipolar junction transistor.Illumination of the base generates carriers which supply the base signal while the base electrode is left floating.The emitter junction constitutes a diode , and transistor action amplifies the incident light inducing the signal current.A photodiode is a semiconductor diode which gives an important photocurrent under illumination. One type of photodiode uses a p-n reverse biased junction operated below the breakdown voltage. Excess charge carriers or electron hole pairs are generated by photoconductivity with exposition to electromagnetic radiation.Carriers usually recombine quickly , but the ones produced near or in the depletion layer of the junction can cross the junction and give a photocurrent which is superimposed on the small reverse saturation current.Photodiodes allow the manufacture of devices with a depletion width convenient for best sensitivity and frequency response.
I found a guy on ebay who had these (276-0142) for sale. I ordered two packages.From the front, same label, looks like the same components.But, on the back - Differences!Anybody want to continue the "conversation"?
Photodiodes are semiconductors that produce current flow when they absorb light. In application, there are two types of photodiodes: 1) photovoltaics and 2) photoconductors.Photovoltaics work like solar cells (in fact they are the same). When light shines on the photodiode, a voltage is created across it, causing current to flow. Photoconductors are reverse-biased photodiodes. When light shines on the photodiode, the resistance to the reverse-bias decreases. By measuring the current through the photodiode, you can detect the intensity of light.
ComparisonFrequency ResponsePhotodiodes are much faster than phototransistors (nanoseconds vs. microseconds)GainPhototransistors have a higher gain. Photodiodes require an amplifier to use.Temperature ResponsePhotodiodes vary less with temperatureApplicationsOptocouplerOptocouplers are used in electronics-sensitive applications. For example, you may use this in a mobile robot application to separate the microcontroller circuitry (low voltage/power) from the motor driver circuitry (high voltage/power).
Photoconductor and it did work to output any current more like a diode that switched with light you could read the resistance change with light.