_
|
.
5—3.
FREE ELECTRONS IN A METAL
103
The latter noises are‘usually more prondunced for audio_than for
.
radio frequenc‘y ampliers. Finally, there exists a thermal noise
which will be discussed …in the next section and which is of the order
of one-third that of the shot effect if there is no space charge. Under
operating condition
of an amplier, a space charge does
'
exist, in which case the thermal noise is considerably greater than
the shot noise.
_
,5—3.
Free Electrons in a
a given sample of metal
there are Small crystals of microscopic size, arranged sometimes in
a haphazard fashion and sometimesin a regular manner, accord—.
ing to the treatment which the metal has received. Frequently
there are _impuritieS in the spaces between the crystals. Each of
the crystals contains atoms arranged in various geometrical congurations or “space lattices,” as revealed by x-ray crystal anal—
,
ysis methods. The atoms are bound in essentiallyxed positions
and contain within themselves electrons which are_in rapid motion.
It
that some of
electrons are able to escape
_
their atoms and move about With more or less
inside
-
‘
the metal. The metal, as a»whole, remains neu‘tral since the neg‘a— '
_
tive charge of the free electrons is counterbalanced—by the pOsitivè
_
__
.
charge of:the atoms from’which they have escaped. The number of
,
a
free
depends on the …eas‘e Ïwith which they
escape
from the atoms; Thus, inÎinsulatbrs there
but
of these
.
_
_
charged carriers,whereas .in_metals there “is One electron per atom,
perhaps even
frée,cto.mçve about.
_
A
in a metal may travel a distance “of several
_
“hundred:
particles.
‘
Changes 1ts velocity andd1æŒ10nThusïefreeelætronsare in aÏ ’
_
cont1nuousstateofüermalag1tatlon,movmg
,
andentenngandleavmgatomsStatistlcallya *C°Iïditi0h 1°f—
*
electnsandtheatomsAtagVHstntthereareslwndfst
electr0nSWlthallgraat10nsbetween l
‘
*
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|
.
5—3.
FREE ELECTRONS IN A METAL
103
The latter noises are‘usually more prondunced for audio_than for
.
radio frequenc‘y ampliers. Finally, there exists a thermal noise
which will be discussed …in the next section and which is of the order
of one-third that of the shot effect if there is no space charge. Under
operating condition
of an amplier, a space charge does
'
exist, in which case the thermal noise is considerably greater than
the shot noise.
_
,5—3.
Free Electrons in a
a given sample of metal
there are Small crystals of microscopic size, arranged sometimes in
a haphazard fashion and sometimesin a regular manner, accord—.
ing to the treatment which the metal has received. Frequently
there are _impuritieS in the spaces between the crystals. Each of
the crystals contains atoms arranged in various geometrical congurations or “space lattices,” as revealed by x-ray crystal anal—
,
ysis methods. The atoms are bound in essentiallyxed positions
and contain within themselves electrons which are_in rapid motion.
It
that some of
electrons are able to escape
_
their atoms and move about With more or less
inside
-
‘
the metal. The metal, as a»whole, remains neu‘tral since the neg‘a— '
_
tive charge of the free electrons is counterbalanced—by the pOsitivè
_
__
.
charge of:the atoms from’which they have escaped. The number of
,
a
free
depends on the …eas‘e Ïwith which they
escape
from the atoms; Thus, inÎinsulatbrs there
but
of these
.
_
_
charged carriers,whereas .in_metals there “is One electron per atom,
perhaps even
frée,cto.mçve about.
_
A
in a metal may travel a distance “of several
_
“hundred:
particles.
‘
Changes 1ts velocity andd1æŒ10nThusïefreeelætronsare in aÏ ’
_
cont1nuousstateofüermalag1tatlon,movmg
,
andentenngandleavmgatomsStatistlcallya *C°Iïditi0h 1°f—
*
electnsandtheatomsAtagVHstntthereareslwndfst
electr0nSWlthallgraat10nsbetween l
‘
*
Theapphcatwn0fanelectromatlVf©fœb€tWænthemdsofä—
Wiresuper1mpœesadumtln@nüethermalmovement80füe
—
thephenwenaofmalhecnuctl®Astreamofwaœfïsaï
'
'
1@W6t@fallmt@@neSI6®fab®WïfuüfwaœfAlm08tlnstantly
;