1.Because of the very high open -loop voltage gain of the op-amp,the output is driven into positive saturation(close to+V)when the sample voltage goes slightly above the reference voltage ,and driven into negative saturation (close to -V)when the sample voltage goes slightly below the reference voltage.

2.Both N-type and P-type semiconductors are made by treated materials,such as germanium and silicon with impurities such as arsenic and indium.

3.By comparison,most other forms of transmission systems convey the message information using the shape,or level of the transmitted signal;parameters that are most easily affected by the noise and attenuation introduced by the transmission path.

4. Digital transmission system-embodied by telegraph systems-were developed in the 1850s before analog systems-the telephone-in the twentieth century.

5.Depending on the relationship between the signal frequencies and the sampling rate,spectral inversion may cause the shape of the spectrum in the base and to be inverted from the true spectrum of the signal.

6.Each element has a separate identity of its own,that is,no two elements have the same physical and chemical properties,nor can an element be subdivided by ordinary physical and chemical means into simple element.