Question about photodiode performance.

[Blapto]

First off, do photodiodes and phototransistors do exactly what they say on the tin? Will they allow current to flow when they detect light?
Second, is the ambient light in a room with the lights on (for arguements sake, one 60W bulb, 10 feet away in an enclosed room) enough to allow current to flow? And lastly, how quick would they respond to the light coming on or off? For example, if I flicked the light switch off and then on again as fast as I could, would that mean that the diode would stop current flowing for a while?
Thanks all.

 

[bmcculla]

Photodiodes do allow current to flow when light is shined on them. They never compleatly stop current. The "dark current" is the amount of current that flows when there is no light at all. They can be quite fast. You can buy 400MHz photodiodes on digikey. To answer your light bulb question you would be able to detect the difference in light as you switch the light on and off. You would even be able to see the filament heating up and cooling off as current was applied or removed.

Brent

 

[Blapto]

A perfect answer! Thanks very much.

 

[Roff]

Photodiodes do allow current to flow when light is shined on them. They never compleatly stop current. The "dark current" is the amount of current that flows when there is no light at all. They can be quite fast. You can buy 400MHz photodiodes on digikey. To answer your light bulb question you would be able to detect the difference in light as you switch the light on and off. You would even be able to see the filament heating up and cooling off as current was applied or removed.

Brent

In fact, you can detect the 120 Hz ripple caused by the filament heating and cooling in response to the 60 Hz power applied.