S3901 Hamamatsu, S3901 Datasheet - Page 4

• Manufacturer Part Number: S3901
• Description: (S3901 / S3904) NMOS Linear Image Sensor
• Manufacturer: Hamamatsu

Figure 5 Spectral response (typical example)
The NMOS image sensor consists of a scanning circuit made
up of MOS transistors, a photodiode array, and a switching
transistor array that addresses each photodiode, all integrated
onto a monolithic silicon chip. Figure 1 shows the circuit of a
NMOS linear image sensor.
The MOS scanning circuit operates at low power consump-
tion and generates a scanning pulse train by using a start
pulse and 2-phase clock pulses in order to turn on each ad-
dress sequentially. Each address switch is comprised of an
NMOS transistor using the photodiode as the source, the
video line as the drain and the scanning pulse input section
as the gate.
The photodiode array operates in charge integration mode
so that the output is proportional to the amount of light expo-
sure (light intensity × integration time).
φ
φ
Construction of image sensor
φ
0.1
0.3
0.2
0
200
400
WAVELENGTH (nm)
600
800
1000
(Ta=25 ˚C)
1200
NMOS linear image sensor
KMPDB0149EA
Figure 6 Output charge vs. exposure
Each cell consists of an active photodiode and a dummy
photodiode, which are respectively connected to the active
video line and the dummy video line via a switching transis-
tor. Each of the active photodiodes is also connected to the
saturation control drain via the saturation control transistor,
so that the photodiode blooming can be suppressed by
grounding the saturation control gate. Applying a pulse sig-
nal to the saturation control gate triggers all reset. (See “Aux-
iliary functions”.)
Figure 2 shows the schematic diagram of the photodiode
active area. This active area has a PN junction consisting of
an N-type diffusion layer formed on a P-type silicon substrate.
A signal charge generated by light input accumulates as a
capacitive charge in this PN junction. The N-type diffusion
layer provides high UV sensitivity but low dark current.
10
10
10
10
10
10
–1
–2
–3
10
2
1
0
–5
φ
S3901 SERIES
10
(Typ. Vb=2 V, V =5 V, light source: 2856 K)
–4
φ
SATURATION EXPOSURE
S3901/S3904 series
EXPOSURE (lx · s)
SATURATION
CHARGE
10
–3
10
–2
S3904 SERIES
φ
10
–1
Ω
10
KMPDB0042EB
0
φ