Tektronix 576 - Page 23

64 . Set t he Ty p e 576 LEF T-O FF-R IG H T switc h to O FF
an d r emove t he universal transistor adap ter from t h
e
Stan d ar d Test Fixture . ( L eave t he transistor in t he a d ap ter) .
Install t he universal FE T adap ter (Te k tronix P a r t Νο .
013-0099-00) on t he Stan d ar d Test Fixture an d p lace an
Ν -c h annel j unction FE T into t h e rig h t test soc k et of t h e
adap te r .
65 . Set t he following Ty pe 576 controls to :
I N T EN SITY

Visible Dis p lay
VER TICA
L 1 mA
VA R IA BLE
CO
LLE CTO R

F ully Countercloc k wise
SU
PPL Y
A
MPL
IT UD
E

.05 V
ST E PS

P resse d
66 . Set t he LEF T-O FF-R IG HT switc h to R IG H T an d
tur n t h e
VA R IA BLE CO LLE CTO R S
UPPL Y control
slowly cloc k wise . Note t h e d is p lay of d rain cu rrent vs .
d rain-source voltage with voltage ste p s of 0 .05 V /ste p
F ig . 2-17 . Dis p lay of FE T co m mo n -so ur ce c h aracteristic cu r ves :
ID
vs . V
ρ
S for 10 ste p s of gate voltage at 0 .05 volts/step
.
a pp lie d to t he gate (see Fig . 2-17) . Since t h
e
ste ps a pp lie d
to t h
e
gate are positive-going, t h
e
curves d is p laye d r
e p
resent
enh a n cement mo d e op eration of t he FE T . ( P ress t he
SI N G LE ST EP F
A M I L Y b
u
tton to locate t h
e
curve
obtaine d wit h zero volts on t he gate .)
67 . P ress t h
e
P O L A R ITY I NVER T bu tton and note t h
e
d is p lay of t h e
d
ep
letion mo d
e
of o p
eration of
t h
e FE
T (see
Fig . 2-17) . ( P ress SI NG LE STEP F A M I LY button for ze r o
bias c u rve .)
68 . Set t h e Ty pe 576 LEF T-O FF-R IG HT switc h to
O
FF .
R
emove t
h
e universal FE
T test a d ap
ter and r ep lace it
wit
h
t h
e universal t r
ansistor
test a
d ap
ter (wit h t he
transistor still in it .)
69 . Set t h e following Ty pe 576 controls to :
O p erati n g Instructions-Ty pe 576
VER TICA L 5 mA
A MPL IT UD E

Current Steps
NUMBER O F STEP S

5
P O L A R ITY I NVER T

R elease d
Set
t h
e
AM PL IT UD E switc h and t he V A R IA BLE
CO LLE CTO R S UPPL Y control
for
α family
of curves
similar to Fig . 2-18 Α .
70 . N ote t he β or
gn u
p
er
d
ivision rea dout . By measuring
t he vertical divisions
between
two
c
u rves of t
he
d is p layed
family, t h
e β
of t
he device in
t
h
at
region can be determined .
For
exam p
le, t h ere is a pp r oximately 0 .9 d ivision between
t he fourt h a n d fift h ste p s s h own in Fig . 2-18 Α . Th e β of t he
device
w
h en o p erate d in t h is region is, t h erefore, a pp rox-
imately 0 .9 (200) or 180 . To ma k e α more accurate
measurement of β , t he d ifference in both collector an d base
c u rrent between t h e fourt h an d fift h ste p s s h o u l d be less .
71 . P ress t he O FF SE T ΑΙ D button an d set t h e O FF SE T
MUL T control to 4 . N ote t h at t he offset cu rr ent has been
a dd ed to t he Ste p Generator o u t p ut so t h at t he zero ste p is
now at t h e level of t he fo u rt h ste p d is p laye d .
72 .
P
ress th
e
ST
EP
MUL T .1 Χ b u tton . N ote t h at th e
current per ste p
is now 1/10 of t h
e
value set by t h e A MPL I-
TU D E switc h . C hec k t h
e
PER ST EP rea d out for t he new
am p litu d
e per
ste
p . (See
Fig . 2-18 Β .)
73 . Set t he DIS PL AY
O
FF
S
E
T Selector switc h to
VER T
Χ 1 and turn t
he
C EN T
E
R L I NE V A LUE switc h
cloc k wise until t he fi r st ste p is with in
±0 .5 d ivision of t h
e
center horizontal line .
74 . Set t
he
DIS
PL
AY O
FF
S
E
T Selector switc h to
V
Ε
R ΤΧ 10 . Note t h at t
h
oug
h
t h
e !3 p er
d ivision is still 200
as it was in ste
p
70,
t he c h
ange in collector an d base current
( Δ Ις and
A[ B)
is less between t he fourt h an d t he fift h ste p .
T h is allows for α more accurate measurement of β at t he
level of
t
h
e
fourt
h ste p (see
Fig .
2-18C)
. T he
β
of
t
he device
at t he fourt h ste p
now
measures at
abo
u t 0
.8 (200) = 160 .
75 . Set t he
following
Ty p
e
576
controls to :
VER TICA L 1 mA
DIS PL AY O FF SET

NORM (O FF )
Selector
A
M
PL IT
U D E

.05 V
NUMBER O F ST EP S

1
O
FF SE T MUL T

0
ST EP Μ UL T

R elease d
76 . Turn t h e O FF SE T MUL T control un til α ste p j ust
begins to a pp ear on t h e CR T . N ote t h e multi p lier value on
t he O FF SE T MUL T control . T h is number times t he AM-
PLITUDE switc h setting is t he base-to-e m itter turn on volt-
age of t he transistor .
2-1 5
ρ
. S MO N N O W = Ζ
~ Μ
PER
Ή !
ν il
PER
Ρ ~ V
PER