THAT1243 ETC [List of Unclassifed Manufacturers], THAT1243 Datasheet - Page 4

• Manufacturer Part Number: THAT1243
• Description: Balanced Line Receiver ICs
• Manufacturer: ETC [List of Unclassifed Manufacturers]

Page 4
differential amplifiers with gains of zero, -3 and -6 dB
respectively, and are primarily intended as balanced
line receivers for pro audio. However, their topology
lends itself to other applications as well.
THAT 1246 configured as zero and -6 dB line receiv-
ers respectively. These devices can be used to retrofit
circuits currently using the SSM 2141, INA134,
SSM2143, or INA137.
THAT 1246 are form, fit and functionally compatible
with their competitors’ equivalent versions, their slew
rate and bandwidth are superior.
Corporation’s line receivers can accept common
mode voltages that exceed the power supply rails.
Consider Figure 2. Assume that the circuit is con-
figured as shown, but with no differential excitation.
In+ and In- are shorted together, as are Vout and
Sense. Ref is tied to ground. a and b will be held at
the same voltage by feedback.
node a is V
V
a maximum common mode input of 29.3 dBu. Un-
der the same conditions, the THAT1243 can tolerate
30.0 dBu and the THAT 1246 can tolerate 32.9 dBu.
These numbers are slightly higher than the datasheet
specifications, since they’re calculated with a slightly
higher supply voltage. Also note that high levels of
common mode input compromise the maximum dif-
ferential mode signal that can be handled by these
ICs.
EE
The THAT 1240, 1243, and 1246 are precision
Figures 3 and 4 show the THAT 1240 and
Like other amplifiers of this type, all of THAT
The maximum voltage allowed at the internal
a
Isolating V
V
Thus, the maximum input in dBu would be
V
With ±18V supplies, the THAT 1240 can tolerate
plus 2V. The voltage at a can be calculated
PK CM
IN
=
max
V
-
PK CM
CC
-
-
dbu
=
minus 2V, while the minimum voltage is
PK-CM
a
[
[
=
R3 R4
R
, we see that
20
4
R4
R
THAT Corporation; 45 Sumner Street; Milford, Massachusetts 01757-1656; USA
+
+
4
R
log
Tel: [phone]; Fax: [phone]; Web: www.thatcorp.com
3
]
]
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While the THAT 1240 and
(
Vcc
-
2
2
V
0775
)
.
´
[
R
4
R
+
4
R
3
]
ù
ú
ú
û
Application Notes
cision summing amplifier. This circuit uses both the
In+ and Ref pins as inputs. Refering to Figure 2, it
can be shown by superposition that the voltage at a
will be
Lo
Hi
Ref
In+
Lo
Hi
Figure 5 shows a THAT 1240 configured as a pre-
a
=
(
In
2
3
+
2
3
2
3
) [
Figure 5. Precision summing circuit
In-
In+
R
Figure 3. Zero dB line receiver
In-
In+
Sense
In-
In+
Figure 4. -6 dB line receiver
4
R
Ref
+
4
R
Sense
Sense
3
Ref
1
Ref
5
]
Vout
+
1
1
R
5
5
ef
Vout
Vout
1246
U1
[
R
Balanced Line Receiver ICs
U1
1240
6
4
R
+
1240
Preliminary Information
3
U1
R
3
6
]
( Hi - Lo ) * 0.5
6
(In+)+ Ref
Hi - Lo