EG&G 113 - Page 20

(2)
M°de|
AM'2
wired to
pin 3. A
BNC connector
should
be
installed
at
the
amplifier
end
of
the cable.
The AM-2 is best
for
high frequency applications.
The
turns
ratio of
this transformer
is
1:100.
Figure
Ill-12A
is
a
family of amplitude
response
curves
for
a typical
Model
AM-2,
and
Figure lll-12B is the
corresponding
family of
noise
figure contours.
In the
transformer-
®\
%1T~'§eie°>'::‘eE-cetggws
1
amplifier
system,
the noise
figure obtained
from
~
Figure lll 12B predominates, and
therefore,
this noise
figure
can
be
regarded
as
the system
overall noise
'-
_
ii’
—
1
figure. However, the transformer
frequency response
5 9
,
‘
:
‘
.
.
. .
9
l
9
6
and amplifier
frequency response
set with
the
rolloff
é
controls
must be
combined to obtain
the system
Q
Q
.
.
9
°
V
overall
response characteristics
'5
tee
in
souacs
—- —-
9
000000000
'-I 120
50
SOURCE '
¢
L
OUTPUT
/77
9 no
ion SOURCE - --- '\
Figure
Ill-13.
MODEL
AM-2
SCHEMATIC,
E0UT/E~TURN
Q
O
O5
O
E100
'°°°s°°"°‘_‘;3r-"
--- ....
..
/
TURNS
RATIO
1:100
'" so
,
t
e
.
to
the
primary
such
that
will
cause
insulation
break-
down
of
the secondary
or
damage
to
the
input
circuit
'
/'
.
T
F\
.".
\
/
-"'
’
\\
1
.
.
V
TOP,-'
,°
\\ '\
'._ \
CAUTION:
Be
very
careful
to
avoid applying
a
signal
40$ 2 5 10* 2 5 105 2
5
10°
O1 ‘EH6
amplifier.
FREQUENCY
NOTE:
Because
the
Model
AM-2
has a
ferrite
core,
Fi9“'°'"'12A'
FREQUENCY
RESPONSE
OF
TYHCAL
core
ma netization
will
not
occur as
a
result
of dc
290K
‘-
O
mu
OHMS)
RATO:00)
CERESS
TURNS
SOURCE
Z5
MODEL
AM-2
TRANSFORMER
g
.
.
.
current.
However,
excessive
dc current
in
the
primary,
along
with
the
ac signal,
may
result
in
premature
IO a
saturation
of
the core
and
distortion
of the
signal.
( MOde|
la
wvss
°°°'° °'=‘°"*
°P"
IIIIIIIIIJI;
‘IjIjIjIjijIfI§5E
crating
in shaded
region
:jIjIjIjIjIjIjIjIjIjIjI'I'I'Ij._._"IjIjIjIjIjIjIjI
_. "
5d
VI
5
The
Model
190
is the
best
transformer
to
use
at very
low
frequencies and
where
good low-noise
perfor-
ldB
mance
is required
at low
frequencies.
This
transformer
T
-‘
r
has two
primary
windings,
P1,
with
a
P1
:P3
turns
ratio
MB
of
121000,
and
P2, with
a
P2:P3
turns
ratio of.
1:100.
~'
/
Only
one
of these
primaries
should
be
connected
at a
\
eds
‘
"t
time,
and
the
unused
winding
left open.
Figure
lll-15
|O-r
\*
/
is
a
family of amplitude
transfer
curves
for the
Model
03
3,rQ3
|Q4
3,
Q4
|Q5
190,
and
Figure
lll-16 is the
corresponding
family
of
noise
figure
contours.
The
noise
figure
contours
are
transformer-amplifier
system
contours,
so
separate
noise
figures
do
not
have
to be
combined.
However,
FREQUENCY(Hz)
Figure
Ill-12B.
NOISE FIGURE
CONTOURS FOR
‘
the
transformer
frequency
response
and
the
amplifier
TYP'cA|-
MODEL
AM"?
TRAN$F°RMER
frequency
response
set
with
the
rolloff
controls
must
be
combined
to
obtain
the
overall
system
response
An output
cable,
made
up with connectors,
and
an
eharaeterietree
input connector
are supplied
with
each
AM-2 manu-
factured. When
ordering
the transformer
remember
to
Note
the
reeenanee
peak
at
the
high
frequeney
end
of
specm’
which
i"$'"'~'me0t
it
is to
be used
With’
5°
that
the
transformer
response
curve.
If the
input signal
has
the
proper
connector can be
provided at
the amplifier
frequency
eernpenente
in
this
range
the
annpher
may
end of the cable.
When making
up cables
for
connect-
he prematureh,
ever|eaded
by
them,
partieu|ar|y
at
509
T0
T09
i0PU’f
80d
‘E0 the QUTPUT,
U59 (380000 bFa0d
high
signal
or gain
levels.
If
high
frequency
signal
W050
¢0009C'E0F$
W09 X|-R'3"11C
OF Xl-"3419,
Or
components
cause
such
problems
the
operator
may
eqUiVa|90'I-
C08Xia| Cab|e
$00U|d
be Used,
PF9f9rab|V
Of
consider
prefiltering
the signal
or
changing
the
source
50°"
|<'-‘09'E0
30d
QT the |°W'0°i$9
Va09'IV
lAf0D0900|
impedance
to
flatten
the
response
curve
in this range.
RG/U type 21-537
or 21-541).
Figure
Ill-13,
the
schematic,
indicates
that the
center
conductor
of the
The
geggndary
winding
has 3
neon
lamp
Qgnnegted
OUTPUT
Cable $00U|d be Wired
Y0 D50
2
80d
the
Shield
across
it.
If too
large
a signal
is
applied
to
the
primary,
Ill-8
--—---.__
l
l
(2) Model AM-2
The AM-2 is best for high frequency applications. The
turns ratio of this transformer is 1: 1 00. Figure 111-12A
is a family of amplitude response curves for a typical
Model AM-2, and Figure
111-12B is the corresponding
family
of noise figure contours. In the transformer-
amplifier system,
the noise figure obtained from
Figure 111-12B predominates, and, therefore, this noise
figure can be regarded as
the system overall noise
figure. However, the
transformer frequency response
and amplifier
frequency response set with the rolloff
controls must be combined to obtain the system
overall response characteristics.
g L~O
::: 120
9110
....
In SOURCE --
2n SOURCE •••••••••
sn SOURCE -.-.
Ion SOURCE - ---
loon SOURCE--
71'\
_r.....;
.,"-
---
\
......
L.- -::.
;;.o.?" '· ...... 7
I- -=-
'r;;:
...
: tOO
~ 90
~ 80
I/~.· .
I
/
I
\ \
I
1\
.... "
-; 70
'"
~
~ 60
~
I.aJ 10'
10" 2 5 10
5
FREQUENCY
Figure 111-12A. FREQUENCY RESPONSE OF TYPICAL
MODEL AM-2 TRANSFORMER
FREQUENCY (HZ)
Figure 111-12B. NOISE FIGURE CONTOURS FOR
TYPICAL MODEL AM-2 TRANSFORMER
An output cable, made up with connectors, and an
input conne~tor are supplied with each AM-2 manu-
factured. When ordering the transformer remember to
specify which instrument it is to be used with, so that
the proper connector can be provided at the amplifier
end
of the cable. When making up cables for connect-
ing
to the input and to the output, use Cannon brand
audio
connectors type XLR-3-11C or XL-3-11C, or
equivalent. Coaxial cable should be used, preferably of
short length and of the low-noise variety (Amphenol
RG/U
type 21-537 or 21-541). Figure 111-13, the
schematic, indicates
that the center conductor of the
output cable should be wired to pin 2 and the shield
111-8
wired to pin 3. A BNC connector should be installed
at the amplifier end of the cable.
BOTH CONNE CTORS
CANNON XLR -3-9JT
Figure 111-13. MODEL AM-2 SCHEMATIC,
TURNS RATIO 1 :100
CAUTION: Be very careful to avoid applying a signal
to the primary such that will cause insulation break-
down of the secondary or damage to the input circuit
of the amplifier.
NOTE: Because
the Model AM-2 has a ferrite core,
core magnetization will
not occur as a result of dc
current. However, excessive dc current in the primary,
along with
the ac signal, may result in premature
saturation of the core and distortion of the signal.
(3) Model
190
The Model 190 is the best transformer to use at very
low frequencies and
where good low-noise perfor-
mance
is required at low frequencies. This transformer
has two primary windings, P1, with a P1: P3 turns ratio
of 1: 1 000, and P2, with a P2:P3 turns ratio of 1: 100.
Only one of these primaries should be connected at a
time, and
the unused winding left open. Figure 111-15
is a family of amplitude transfer curves for the Model
190, and Figure 111-16 is the corresponding family of
noise figure contours. The noise figure contours are
transformer-amplifier system
contours, so separate
noise figures
do not have to be combined. However,
the transformer frequency response and the amplifier
frequency response
set with the rolloff controls must
be combined to obtain the overall system response
characteristics.
Note
the resonance peak at the high frequency end of
the transformer response curve. If the input signal has
frequency
components in this range the amplifier may
be prematurely overloaded
by them, particularly at
high signal or gain levels. If high frequency signal
components cause such problems the operator may
consider prefiltering
the signal or changing the source
impedance
to flatten the response curve in this range.
The secondary winding has a neon lamp connected
across it. If too large a signal is applied to the primary,
)