Question

Comprehension

Direction: Read the Passage and Answer Questions

Charge Couple Device (CCD) can be used either as an image sensor or as a shift register. As a photo detector it has also been called charge - coupled image sensor or charge - transfer image sensor. Most common area images use either interline transfer or frame transfer readout architecture. The spacing between CCDs should be small for efficient charge transfer.

Give below are two statements:

Statement 1: The three basic charge - transfer mechanisms in CCD are (a) thermal diffusion (b) self - induced drift and (c) fringing - field effect.

Statement 2: For small amount of signal charge, self induced drift is the dominant factor and for a reasonably large charge packet; thermal diffusion is the dominant transfer mechanism

In the light of the above statements, choose the correct answer from the options given below

(1) Both Statement 1 and Statement 2 are correct

(2) Both Statement 1 and Statement 2 are incorrect

(3) Statement 1 is correct but Statement 2 is incorrect

(4) Statement 1 is incorrect but Statement 2 is correct

1. 1
2. 2
3. 3
4. 4

Answer 1

Correct Answer - Option 3 : 3

Statement 1 Explanation- In CCD  four mechanisms are involved in the dynamic charge transfer process

• Self-induced drift                            
• Electrostatic repulsion
• Thermal diffusion
• Fringing field
   

The first charge carriers are transferred by self induced drift and thecharge is re-distributed within the well by electrostatic repulsion Bothprocesses are fairly quick. Thermal diffusion is a slower process. Finally, the last remaining charge is transferred by fringing field. So statement 1 is correct.

Statement 2 Explanation- Self-induced drift is a charge repulsion effect which is important for large signal-charge densities. Thermal diffusion is caused by the strong gradient of the signal-charge at the edge of the transferring electrodes.So statement 2 is incorrect.

So option (3) is right answer.