Photodiode Series with Cap

Greetings all,
I want to know is it possible that a photodiode be series with a capacitor? And what that means?

Please see attached image

Thanks

qse773.png

The cap is blocking D.C., in this case. A change in signal will be passed. A, common way, to isolate one part of a circuit from another part.

Idahowalker:
The cap is blocking D.C., in this case. A change in signal will be passed. A, common way, to isolate one part of a circuit from another part.

That means by default a photodiode when producing current, the capacitors is in change mode and when current drops, capacitor will be dechange. right?

Maybe the designer was only interrested in fast light changes, not in static (sun)light.
Example is measuring the speed of a propellor of a remote controlled airplane.
Then you want to block static light (DC from the photo diode),
and only amplify the light changes from the propellor blades (AC ripple on top of the DC).
Another example is the pulses from a remote control.
You only want the remote control pulses, not the static light in the room.

You might want to study capacitors and high-pass (or low-pass) filters,
so you understand at what frequency this blocking/passing occurs.
Leo..

navab1362:
That means by default a photodiode when producing current, the capacitors is in change mode and when current drops, capacitor will be dechange. right?

As the input to the cap changes, rises or falls, the change will be reflected across the cap.

Wawa:
Maybe the designer was only interrested in fast light changes, not in static (sun)light.
Example is measuring the speed of a propellor of a remote controlled airplane.
Then you want to block static light (DC from the photo diode),
and only amplify the light changes from the propellor blades (AC ripple on top of the DC).
Another example is the pulses from a remote control.
You only want the remote control pulses, not the static light in the room.

You might want to study capacitors and high-pass (or low-pass) filters,
so you understand at what frequency this blocking/passing occurs.
Leo..

Absolutely right,
This circuit used for a ballistic chronograph (calculate projectile speed). Projectile speed is high and so changing in light is too fast.
Thanks a lot Wawa

Idahowalker:
As the input to the cap changes, rises or falls, the change will be reflected across the cap.

Thank you Idahowalker for your useful reply.