Analog Electronics

1/ ENERGY BANDS IN SOLIDS

In this chapter we begin with a review of the basic atomic properties of

matter leading to discrete electronic energy levels in atoms. We find

that these energy levels are spread into energy bands in a crystal.

This band structure allows us to distinguish between an insulator, a

semiconductor, and a metal.

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CHARGED PARTICLES

The charge, or quantity, of negative electricity and the mass of the

electron have been found to be 1.60 X 10- 19 C (coulomb) and

9.11 X 10- 31 kg, respectively. The values of many important physical

constants are given in Appendix A, and a list of conversion factors and

prefixes is given in Appendix B. Some idea of the number of electrons

per second that represents current of the usual order of magnitude is

readily possible. F'or example, since the charge per electron is

1.60 X 10- 19 C, the number of electrons per coulomb is the reciprocal

of this nutnber, or approximately, 6 X 10 18 Further, since a current

of 1 A (ampere) is the flow of 1 Cis, then a current of only 1 pA (1 picoampere, or 10- 12 A) represents the motion of approximately 6 million

electrons per second. Yet a current of 1 pA is so small that considerable

difficulty is experienced in attempting to measure it.

The charge of a positive ion is an integral multiple of the charge

of the electron, although it is of opposite sign. For the case of singly

ionized particles, the charge is equal to that of the electron. For the

case of doubly ionized particles, the ionic charge is twice that of the

electron.

The mass of an atom is expressed as a number that is based on the

choice of the atomic weight of oxygen equal to 16. The mass of a

hypothetical atom of atomic weight unity is, by this definition, onesixteenth that of the mass of monatomic oxygen and has been calculated to be 1.66 X 10- 27 kg. Hence, to calculate the mass in kilograms

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2 / INTEGRATED ELECTRONICS

Sec. J-2

of any atom, it is necessary only to...