Circuit
Description
—
Type
575
Fig.
3-14.
Simplified
diagram
of
the
Step
Amplifier
for positive-going
current
steps.
30
to
1
divider;
a
15-volt
step
in the positive
direction
at
the
top
of
R202
will
therefore
produce
a
0.5-volt
step
in
the
neg
ative
direction
across
R246.
If
the
voltage
at
the
lower
end
of
R246
changes,
the
volt
age
at
the
top
of
R246
must
change
the
same
amount
and
in
the
same
direction.
This
will
insure
that
the
voltage
drop
across R246
is
proportional
only
to
the
input
step voltage.
The
+1
Amplifier
is
a
feedback amplifier
whose gain
is
just
slightly
greater
than
unity.
The
input
impedance
of
this
circuit
is
very
high,
so
that
it
does
not
load
the
input
of
the
transistor
under
test.
Let
us
assume
that
the
voltage
at
the
lower
end
of
R246,
and
hence
at the
grid
of
V254,
goes
in
the
positive direction.
This
will
cause
the
cathodes
of V254
and
V264
to
go
in
the
positive
direction.
The voltage at
the plate
of
V264
will then
go
up
carrying
with
it
the
voltage
at
the
grid
and
cathode
of
V233B.
Because
the
gain
of
the
circuit
is
slightly
greater
than
unity
the
change
in
voltage
at
the
cathode
of
V233B
will
be
slightly
greater
than
that
at
the
lower
end
of
R246,
but
will
be
of
the
same
polarity.
The
output
of
V233B
is
applied
to a
divider
consisting
of
R273,
R274
and
R275.
One
tap
on
the
divider
couples
al
most
all
of
the
output
voltage
back
to
the
grid
of
V264.
This
causes
the
grid
of
V264
to
move
in
the
same
direction
as
its cathode,
and
hence
reduces
the
gain
of
the
stage
to
just
slightly
greater
than
unity.
The
gain
of
the
+1
Ampli
fier
is
therefore
relatively
independent
of
tube
characteristics
and
is
determined
almost
entirely
by
the
ratio
of
R273
to
R274
+ R275.
The
resistance
values
in
the
divider
are
chosen
so
that
the
change
in
voltage
at
the
top
of
R275 is
the
same
as
that
at
the
grid
of V254 (the
lower
end
of
R246).
This
positive-going
voltage
at
the
top
of
R275 is
then
applied
to
the
grid
of
V224,
and
the
cathodes
of
V224
and V214
go
in
the
positive
direction.
This
causes
the
voltage
at
the plate
of V214
to
go
up,
and
since there is
no
polarity
shift
in V233A
or
the
emit
ter-followers,
the
voltage
at
the
top
of
R246
will
go
up.
Thus,
the
voltage
at
the
top
of
R246
follows
any
voltage
change
that
may
occur
at
its
lower
terminal. This
prevents
any
change
in the
voltage
at the
input
of
the
transistor under
test
from affecting
the
current
through
R246,
and
provides
for
steps
of
constant
current
into
the
input
of
the transistor.
If
voltage
steps
are
desired,
R249
(not
shown
on
Fig.
3-13)
is
connected between
R246
and
ground.
The
current
steps
through
R246
and
R249
then
produce
voltage
steps
across
R249
which
are
coupled
through
the
series resistor
R248
(not
shown)
to
the
input
of
the
transistor
under
test.
When
negative steps
are
required,
the
voltage
steps
at
the
top
of
R246
must
be
reversed
in
polarity
from
those
at
the
input
(positive-going
steps
are
always
applied
to
the
input
of
the
Step
Amplifier).
The
180-degree
shift
in
signal
polarity
is
accomplished
in
V214,
since
this
stage
is
a
plate-loaded
amplifier.
And, since
V233A
is
a cathode-follower and
the
transistors
are
connected
as
emitter-followers,
the
polarity
shift
in
V214
satisfies
the
circuit
requirements.
When
positive-going
steps
are
required
at
the
top
of
R246,
however,
the
output
of
V214
must
be
reversed
in
polarity.
This
is
accomplished
by
reversing
the
output
and
ground
3-10
Summary of Contents for 175
Page 4: ...VWTICM OINltAlO TRANSISTOR CUM TRACfR UB l COUlClO r hokizoniai VCKIJ O lUnK Hix M Type 575 z ...
Page 6: ...NOTES ...
Page 26: ...NOTES ...
Page 48: ...NOTES ...
Page 54: ...Recalibration Type 575 C706 Fig 5 3 Left Side View 5 6 ...
Page 56: ...NOTES ...
Page 100: ...INPUT AMPLIF1E ...
Page 104: ...TYPE 575 TRANSISTOR CURVE TRACER ...
Page 108: ...OSCILLATOR 4OOV UNREG TYPE 575 TRAN5I5TOR CURVE TRACER AB ...
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Page 119: ...Type 175 Tent S N 570 PARTS LIST CORRECTION Change to Q233 151 0137 00 2N21U8 MIO 298 1165 ...