Re: Autoguider reference

Chuck Grant (grant@aretha.llnl.gov)
Mon, 1 May 95 19:29:57 -0700

> From: aart@uiuc.edu (Aart Olsen)
>
> Of course CCDs are just collections of photodiodes and they get by.

Is this true? I thought they were completely different effects. I thought photodiodes were operated reverse biased and a photon caused current to flow across the junction. The inital electron knocks others out of the semiconductor latice on the way by causing an avalanche, yielding a reasonable number of electrons per photon. This current was then amplified to give a signal, real-time.

Where as a CCD is operated more like a capacitor, unbiased, and it builds up a charge with each additional photon (ideally). After a period of charge integration this cumulative charge is then shifted off and measured.

So can photodiodes be operated in "integrating-mode"?

Chuck