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A
A
4-I.
GENERAI. DESCRIPTION.
4-2.
The
Models
461A and
462A
Ampliliers arc
es-
s€ftiaUy
identical. In
the Model 462A some
of
the
component
values
ar€
cbanged
slightly
to
improve
its
pulse respons€. In
tht
section both
instrumentswiU
be
presented
in terms
of
the
Modet
461A.
4-3.
Figue
4-1 shovs
a
simplilied block
diagram of
theModel461A.
The
amplifier
is
a
five stage,
stagge!-
tuned,
cascadedamplifiervith emitter follower
input
and output
stages.
Th€
ga.in
ia
ewitch€d
frcm
40
db
to20
db
by attenuating
the
lnput
by
20
db.
The power
supply is
a
conventiona.l
seri€s legulat€d
supply
with
+15
volt
and -15
volt
outputs.
4-4.
AItIPUFtER
CTRCUll5.
4-5.
Fieure 5-l38hov,/sthe
schematic
diagram
of
the
Modet
461A.
A3Q3
is
the input
emitter
follower,
matching
the
50
O
input
impedance to
the input impe-
dance
of
the
amplilier.
Transistors
A3Q4
throush
A3Q8
constitute a five 3tage, Rc coupled,
cascaded
amplilier.
Each
stage
bas
a gain of
8
dbr
giving
th€
aJnplilier
a
to&l
gain
of
40
db.
4-6.
Each stage
haa
an LR
feeatback
circuit
*ith
an
adju8table
inductor.
The
feedback
circuit in
each
stage controle
the
overau
gain
of
the
amplifier
at
a
diJferentirequency,
so
the
arplifi€r
nust
be
stagger-
tuned.
There
is
some
intenction
between
the
stages
at cefiain fr€quencies.
A3Qg
is
the
output
emitter
follower,
and
it
matche€
the
amplilier
output to
a 50f,
4.7.
POWER 5UPPI.Y.
4-8.
The power supply genentes
+15
vons
and
-15
volts bias
supply to the
ampriJiers. BreaMoMdiode
A2CR3
estamishes
a
l5volireference.
C
ontrol
transis-
tor
A2Q2
detects diflerences
between
the rcference
voltage
and
the supply
output,
and
iis
output controls
the
series re$rlator
Q1.
M.'dels
461A/462A
sECrtoN lv
THEORY
O'
OPERATION
Section
lV
Parasraphs
4-l
to
4-8
llNArr-l
t6Giffil
satTcH
51,s3
SERIES
REGULATED
Ql-03
/\
01358-2
Figure
4-1.
Simplified Block Diagram
4-l
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