PI0128WSN, PI0256WSN, PI0512WSN

Engineering Data Sheet

Page 2 of 8

Revised March 21, 2002

Figure 2. Geometry and layout of photodiode pixels.

During normal operation, the photons incident in or

near the NP photodiode junction generate free charges

that are collected and stored on the junction's depletion

capacitance. The number of collected charges is

proportional to the light exposure. Figure 3 shows the

stored signal charge as function of light exposure at a

wavelength of 575 nm. The exposure is the product of

seconds. The charge accumulates linearly until reach-

ing the saturation charge, and the corresponding

exposure is the saturation exposure.

The responsivity may be calculated as the saturation

charge divided by saturation exposure. The predicted

at 575 nm. Figure 4 shows the predicted responsivity

of the photodiodes as a function of wavelength.

0

10

20

30

40

50

60

70

80

0

50

100

150

200

250

Saturation

Charge

Saturation

Exposure

Figure 3. Stored signal charge as function of exposure at

a wavelength of 575 nm.