Transfer Of Electric Charge By The Horizontal Ccd - Epson PhotoPC3100Z Service Manual

PhotoPC 3100Z

2.2.1.5 Transfer of Electric Charge by the Horizontal CCD

The transfer system for the horizontal CCD employs a 2-phase drive method.
The electric charges sent to the final stage of the horizontal CCD are transferred to the
floating diffusion, as shown in Figure 2-8.
Figure 2-8. Horizontal Transfer of CCD Imager and Extraction of Signal
RG is turned on by the timing in (1), and the floating diffusion is charged to the
potential of PD. The RG is turned off by the timing in (2). In this condition, the floating
diffusion is floated at high impedance. The H1 potential becomes shallow by the
timing in (3), and the electric charge now moves to the floating diffusion.
Here, the electric charges are converted into voltages at the rate of V = Q/C by the
equivalent capacitance C of the floating diffusion. RG is then turned on again by the
timing in (1) when the H1 potential becomes deep.
Operating Principles
Voltage
Thus, the potential of the floating diffusion changes in proportion to the quantity of
transferred electric charge, and becomes CCD output after being received by the source
follower. The equivalent circuit for the output circuit is shown in Figure 2-9.
Reset gate pulse
Direction of Transfer
H resistor
Electric charge
Floating diffusion gate is
floated at a high impedance.
Figure 2-9. Theory of Signal Extraction Operation
Circuit
Revision A
12V Pre-charge drain bias(PD)
Voltage output
C is charged
equivalently
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