I
f
Load Line" in parallel with the test load line, but
intersecting the zero le line at the rated operating
V c for the transistor. Pick three successive curves
which represent the normal operating base current
region for the transistor, probably those with the
most even spacing. Measure and compare the
change in collector current (6 Id between the
curves along the operating load line. If, for example,
measurements are made between the 1st, 2nd and
3rd curves, measure the 6 le between the 1st and
2nd curves, then between the 2nd and 3rd curves.
Finally, compare the two measurements of
6
le.
If the 6 le are equal. the transistor is operating
A
10 , .......... , ........... , ........... , ........... ;···········,·············--
., ........... , ........... ,
..........
[
9(
8i·--·:;;;--··;,;;;·
__.:;..-+-�--""····-r,::
............ , ........... , ........... ,
............
,
...........
,
j
'
Is•40i,A
7!·'-""""'�.,,.,;,,:;,,,;,,,,+.,�=
le= 30µA
6
i..,,.,.,,,,,,,��=�t:'.'.t'.
.........
L. .......
L ........ L
i
Ic
5
1� 20�A
4 ..........
,
........... , ........... , ...........
,
...........
,
...........
,
...........
,
...........
,
...........
,
...........
,
21
..........
,
...........
,
...........
,
........... , ........... , ..........
0 .......... ; ........... ; ..........
+ ..
·····--·i
.
2 3
4
5
6
7
8
9
W
Ve
NON -LINEARITY
GAIN DECREASES AS
Ic
INCREASES
in a linear region and does not introduce distortion.
If 6 1
0
's are imbalanced, distortion will be intro
duced due to this non-linearity. The greater the im
balance, the greater the distortion.
The distortion measurement can be analyzed by
examining the application of a signal such as a
sinusoidal wave to the transistor which has its fam
ily of curves displayed in Figure 20. Assume a
quiescent state bias of 20 p.A and a 20 p.A peak-to
peak signal variation, 10 p.A above and below the
20 p.A static bias. As the signal swings positively,
to an instantaneous base current of 30 p.A (3rd
curve), the collector current increases from 4 mA to
10
9
, ..........
8
{
7
i
i
.
'
I
11
•.5111A
i
I
I�=.4mA
B
Ic
:5•··f+··········,
.....
, .....
,
.....
,
i
.....
,
.....
,
!
......
;
..... ; ..... , ....
;
.....
:
..... :
....
,
.....
; ..... , .....
!
.....
; .....
,
l&;3111A
4�, .•
_
..... ....;.._,___,__,__ ................. ...,.
........
,
........ ..
'
3 ......... -.. .
.
...
,
....
;
..
,,
.. ...
:
...........
:
..........
:
......... .
,
·1� =.2111A
2
l'.'.'.:::::t::::::::::t::t.::t.,:::=r.::t,::t::t:-
....
j
... ......
.
19•.lmA ·:··
le=O
l
2
3
4
5
6
7
8
9
10
Ve
NON -LINEARITY
GAIN INCREASES AS le INCREASES
Figure 19. Current Gain Non-Linearity
le
\
10
,
·
···
··
·
·
·
r
·
··
·
·
·
y
·
·
·
···
·r·
·
··
·
·
·
·
·
:
g[. le
•
_
5011A
.
\.
.
i
;
:
:
5;
..
·x�=40�A\j
\
7f
\
6
i·
.
...
.........
\
....
: ..........
'
.......... , ... .
i\
,:
'
'
.......
\
.. .; )
. ...
•
..
)
\\
Ve
%
�
,:
·
·
··
\
i,
18 20
2
4
6
s
yo
12 14 1&
RATED OPERATING VOLTAGE
\
G>
1c>
<:.-
�
�
<
..,
�
Figure 20. Measuring Current Gain Non-Linearity
OUTPUT SWING
17
