Tektronix CURVE-TRACER 576 Instruction Manual page 70

Circuit Description-Type 576
OPEN
SHORT
1
1\\
-
'
\
o Vertical
Display Switching
1short not available
\
Standard Test
Fixture Schematic
EMITTER
GROUNDED
BASE
GROUNDED
Note
in BASE GROUNDED
position.
Pin numbers refer
to connector J360
500nA
1 nA
To Horizontal
Display Switching
Pins
11, 12, 27
Collector
Supply
Output
Collector
Supply
Current
Return
Pins
13, 28, 29 Guard Box
»
Display Sensitivity
Switching Schematic
Note { RA'
overlap RB'
R401 through R409
R433 through R438
R439 through R440 (or open)
R442 through R444
R442 through R445
Fig. 3·10. Simplified schematic of Display Sensitivity switching and Standard Test Fixture schematics for measurement of emitter current (IE)
collector-base current (ICBQ) collector-emitter voltage
(V
CE) or collector-base voltage
(V
co>·
varying the value of this current sensing resistor (Rs). the
deflection factor of the display on the CRT may be varied.
Leakage Current Sensing.
If the MODE switch is set to
LEAKAGE, emitter current (IE) or collector-base current
(leBO) is measured on the vertical axis of the CRT. Emitter
current is measured by placing a leakage current sensing
resistance (R Ll between the emitter terminal of the device
under test and ground, and measuring the voltage developed
across it (see Fig. 3-10). If emitter current is to be meas-
ured, the TerminAl Selector switch must be set to
GROUNDED EMITTER BASE TERM OPEN or BASE
TERM SHORT. When the Terminal Selector switch is set to
BASE GROUNDED EMITTER TERM OPEN, collector-
base current is measured on the vertical axis. In this case
the current sensing resistor is connected between the base
terminal and ground. As when measuring collector current,
the deflection factor of the display, when measuring emit-
3-16
ter current and collector-base current, can be varied by
varying the current sensing resistance. It should be noted
that the deflection factor of the vertical display is always
decreased 1000 times when the MODE switch is set to
LEAKAGE and the collector supply operates in its DC
mode.
Voltage Sensing Normal Mode. Either collector or base
voltage may be measured on the horizontal axis of the
CRT, depending on the position of the HORIZONTAL
switch. When the HORIZONTAL switch is in its COLLEC-
TOR range, voltage is measured between the collector and
emitter terminals of the device under test, VeE (Terminal
Selector switch set to EMITTER GROUNDED). or between
the collector and base terminals, VcB. (Terminal Selector
switch set to BASE GROUNDED). When the HORIZON-
TAL switch is in its BASE range, voltage is measured be-
tween the base and emitter terminals, VBE (EMITTER
GROUNDED), or between the emitter and base terminals,
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