Tektronix 1A5 Instruction Manual page 18

Operating Instructions — Type 1A5
parison Voltage Range, the maximum input voltage range
and the deflection factor will s
described.
F i gures 2-9B, C and D illustrate three of the 18 poss
VOLTS/CM control s et tings.
TYPE 1A5 DIFFERENTIAL AMPLIFIER
BLOCK DIAGRAM
A basic unders ta nding of the equipment being us
us e ful in determining just what the ins
doing. A s t udy of the block diagram information which
follows should prove helpful in operation of the Type 1A5.
Refer to F i gure 2-10. The Type 1A5 can be broken down
into three principle s ect ions, namely the
input amplifier and the output amplifier. The " front end"
controls the input coupling, attenuation factor, mode of
operation, and comparison voltage.
rejects common mode s i gnals and ampli
s i gnal (or the active differenial probe s
The output s ect ion is concerned primarily with s
fication, providing a push - pull output to the osc
Two es sen ti al ly identical s
the A and B channels, are contained in the Type 1A5. A
pos i tive s i gnal applied to the A INPUT will result in a s
nal passing through the A channel, applying a positive s
nal to the os c il los co pe ' s upper deflection plate, causing
upward deflection of the CRT trace. A pos
plied to the B INPUT will pass through the B channel,
resulting in a n eg ative s i gnal to the upper deflection plate,
causing downward deflection. (A s
will s i mu l taneously be applied to the CRT's lower deflec ­
tion pla te . )
R efe r to F i g. 2-11. The channels are equipped with cou ­
pling switches that operate independently of each othe
They determine which part of the s
channel: AC — only the AC component; GND — none; DC
both the AC and DC componen
to the at tenuato r s, which are an integral part of the deflec ­
2-10
Fig. 2-10. Type 1A5 basic block diagram.
t ill be indicated as previously
i ble
e d is
t rumen t can and is
"fr ont end ", the
The input amplifier
fi es the remaining
i gnal, if selected).
i gnal ampli ­
i lloscope.
i gnal channels, referred to as
i
i
i tive s i gnal ap ­
i gnal of opposite polarity
i gnal will pass into the
—
t s. The s i gnal is presented
tion factor (VOLTS
attenuators s t ep in unison whenever the VOLTS/CM switch
is moved through an attenu
s e lected attenuator routes the s
P LA Y switch. If the DISPL
ne l 's s i gnal, the other channel is automatic
to the COMPARIS O
work can s up ply 0 to 5 V DC of either polarity, or a fixed
0 voltage, as determined by s
AMPLITUDE controls.
deflection will be affected only by the s
nal. If + or — P O LARITY is s
tion will be opposed if Vc is of the s
s i gnal, or aided if Vc is opposite to signal polarity. The
Vc voltage does not pass through the attenuator s
When compared against an input s
through an at t enuator, Vc is equivalent to the basic value
of Vc (0 to 5 V) mu lt
See F i g. 2-8.
If the DISPL A Y switch is pos
tion, both the A INPUT and B INPUT s
cepted by their respective channels and CRT deflection
will be a result of their diffe
CRT pres e n ta tion in A-B mode.
S i gnals from the A and B channels are made available
to contacts of the Differential P
g ­
processed whenever Differential
g ­
s e lected. (In Differential P
P ro be s i gnal received at the relay will have been processed
by the probe in a manner s
A-B mode in the preceding explana
R ega rdless of the s
s ect ion will determine the di
processed by the two input channels and convert it to a
push - pull voltage which will be amplified by the double ­
ended output amplifier.
r .
STEP ATTEN BAL and PR
for un d es ira ble trace sh
and will be discussed in more detail in the Circuit Des
tion s e c t ion.
/ CM) switch. The A and B channel
a tor s w itching position.
i gnal to contacts of the DIS ­
A Y switch accepts only one chan ­
a lly connected
N VOLTAGE (Vc) s ect ion. The Vc net ­
et tings of POLARITY and
If 0 POLARITY is s el ected, the CRT
e lected input sig ­
el ected, the CRT s i gnal deflec ­
a me polarity as the
i gnal which has passed
iplied by the attenuation factor in use.
i tioned to s e lect A-B opera ­
i gnals will be ac ­
r ence . Vc cannot affect the
r obe relay and will be
P ro be operation is not
ro be operation, the Differential
i m i lar to that desc
ti o n. )
o urce, a comparator in the amplifier
f fe r ence between the s
O BE STEP ATTEN BAL adjust
i ft caused by circuit unbalances
The
ect ion.
ri bed for
i gnals
cr ip ­