Can photodiodes substitute for solar cells(NOT panel)

Of course. Just connect to a meter in Volts mode and shine a bright light on a photodiode, or even an LED! You will get a voltage, and can draw photocurrent from it. Many systems use sensor photodiodes and LEDs as light sensors this way, rather than reverse-biased.

Now, this may not be an efficient way to generate power, but as a sensor, they work fine this way.

Jon

If you use those diodes to limit the input voltage between 0 V and Vcc from a very high impedance source, the voltage will go crazy, if only one of those reverse biased diodes are illuminated due to the photo current.

Use non-transparent diodes to limit the voltage from a high impedance source.

Solar cells are basically low-quality photodiodes with low series resistance. You don't care about the leakage of a solar cell, since it's forward biasing itself anyway.

Turning the question around, I've used solar cells as photodiodes in measurement gizmos on occasion, because you can get a lot of area for cheap. Their capacitance per unit area is fairly horrible, but if you cascode them with a common base input stage, you can use them quite successfully up to 20 kHz or so.

Cheers

Phil Hobbs

The 1N4148 is both a package and electrical spec. I assume there was a time that package and electricals had one JEDEC number. Anyway, that is why they are still made in glass. Obviously at some point in time, the part number standard became such that the number represented the electricals and a suffix indicated the package. Not my job, so if someone is a guru on this, I'm all ears.