Tektronix 576 - Page 28

O p erating 1 n st ι u ctio n s-Ty pe 576
Wh en emitte r c u rrent is being measu r e d by t he ve r tical
d is p lay, t h e only
significant measurements made by t he
ho r izontal d is p lay are
VICE
an
d V ςΒ . To ma k e t h ese meas-
ur ements, t he H O
R IZO N TA L switc h is set with in t h e
CO LLE CTO R ra n ge and t h e Terminal
Selector switc h is set
to EM ITT ER GR O UN DED or BAS
E
G R O
UN D E D .
W it h t h e VER TICA L switc h set
betwee n 500 ηΑ /
d ivisio n and 1 ηΑ / d ivisio n , an e r ror occ
u rs in t he h orizontal
measurement . Table 2-3 in d icates
the d egree of t h is erro r in
voltage p er d ivision of vertical d eflection
for
all
t h e setti n gs
of
t he VER TICA L switc h wit h in t h is given
range . U sing t h is
table an d t he following p roce d u r
e, t he actual
VICE
or V ς5
can be cal u clate d .
' EMI T
TER
current,
DIS PLA YO FF S ET Selector switc h set to
NORM (O
FF ) .
1 . Measure t he vertical d eflection of t h
e
d isplay in d ivi-
sions (see F ig . 2-21) .
volts .
2 . Meas
u
re
t h e h orizontal deflection of t he d is p lay i n
3 .
U
si
ng Table 2-3, find the error
factor for the setti ng
of the VER TICA L
switc h and multi p ly it by t he value d
e-
termine d in
ste p 1 .
;Leak
V oltage e rr o r = 3 d ivisio ns Χ 25 m
V =75mV
VICE
= 325
mV - 75 m V = 250 mV
έ Ι
Τ 11
Α
υιν
PER
Η
Ο
R
4 MV
νΕ R
s
Ρ
β
PER
οιν
Fig . 2-21
. Sample calculation o f error in co ll ector to emitter voltage
inc u rred w h en measuring
lea k age o f α tra n sisto r .
2- 20
TA BLE 2-3
Error i n H orizo n tal Voltage
Measurement
P er Divisio n of Ve r tical Deflecti o n
4 .
Subtract
t he voltage d etermine d in step 3 from t he
voltage determined in ste p 2 to give t he act u al
V ςΕ
or
VC B .
Wh en the H O R IZO N TA L switc h is set to ST EP G EN,
ste p s in d icating t he Ste p Generato r out p ut a r e dis p laye d
horizo n tally . T he h orizontal dis p lay s h ows one ste p pe r d i-
visio n and t he am p litu d e of each ste p , as sh own by t he PER
ST EP rea d out d etermines t he h orizontal d eflection factor .
T he h orizontal deflection facto r can be increased by 10
times
for any
of t h e p r eviously mentione d measurements
by setti n g t he DIS PL AY O FF SET Selector switc h to
H OR IZ Χ 10 2 . T he magnified horizo n tal d eflection can be
d etermined eit he r f r om t he PER H O R IZ DI V r ead out or by
d ivi d ing t he setting of t he H O R IZO N TA L switc h by 10 .
M easurements
Table 2- s
h ows t he measu r ements w h ic h are being ma de
vertically and
h orizontally by t he d is p lay for t he va r ious
p ositions of t
he VER TICA L switc h , t he H O R IZO N TA L
switc h and t he Te r mi
n
al
Selecto r switc h . T h ose switc h p osi-
tion combinations
not cove r e d by t he table are not con-
si d e r ed u seful .
Dis p lay Offset an d
M agnifier
T
he
DIS PL
AY
O
FF S E
T
Selector switc h and t he
C EN T ERL I NE VA LUE switc h provides α calibrate dd is p lay
offset of f r om 0 to 10 d ivisions (0 to 100
divisions
w
hen
t h e d is p lay is
magnifie
d ) an d α 10
times
d
is p
lay
magnifie r .
T
he
d isplay
offset
an
d t he
d
is p lay magnifier, w hen in op era-
tion, effect t h
e
d is p lay
eit h er vertically or h orizontally, but
neve r t he w h ole d is p lay . U se of t h
e
calibrate d
isplay offset
is d isc u sse d in t h e P ositio n ing section . U se of the magnifier
is discusse d in both t h e Vertical an d H orizo n tal M eas u
re-
ment and
Deflection Factor sections .
Collector Su
pp ly
T h
e Collecto r Su pp ly p rovides operati ng voltage for t he
d evice und er test . It is α va r iable voltage in t he form of
eit h er α sine wave, o r α full-wave r ectified sine wave
(see
F ig . 2-22) . T his voltage is a pp lied to t h e collector terminals
of t
h e
Sta n dar d
Test F ixture .
T he MAX PEAK VO
L
TS
switch an d t he VA R IA BLE
CO LLE CTO R
S UPPL Y control determine t he p ea k voltage
out p ut of t he Collector S u pp ly, w h ic h may be varie d from
0 volts to 1500 volts . T h e MAX PEAK V O L TS s w itc h p r o-
vi d es fo u r p ea k voltage ranges : 15 volts, 75 volts, 350 volts
and 1500 volts . T he VA R IA BLE CO LLE CTO R S UPPL Y
allows con ti nu o us voltage va r iation of t he peak voltage
wit h in eac h p ea k voltage range .
T h e PEAK
P
O WER W ATTS switc h , w
h
ich interloc ks
wit h t h e MAX PEAK V O L TS switc h , d etermines th e maxi-
mum power out p u t of th e CollectorS u pp ly . P ower o utp ut
2 Th e Horizontal
di s p lay is not cal i brated when t h e VERTIC AL
sw
i
tc h is set
betwee n 100 ηΑ and 1 ηΑ EMI TT ER .
VER TICA L Switch Setting' Voltage
Error P
er
Vertical Division
50 ηΑ , 5 ηΑ 125
mV
20 ηΑ , 2 ηΑ 50 m V
100 ηΑ , 10 ηΑ , 1 ηΑ 25
mV
0 . Α
,
~~
3 ηΑ
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