that1240 THAT Corporation, that1240 Datasheet - Page 7

• Manufacturer Part Number: that1240
• Description: Balanced Line Receiver Ics
• Manufacturer: THAT Corporation

Document 600035 Rev 04
conversion (degrading CMRR) when there are even
slight differences in gain between the VCAs. A better
approach is to convert the signal to single-ended,
alter the gain, and then convert back to balanced.
receiver to do the balanced-to-single-ended conver-
sion. The VCA section also has a static gain of -3 dB
due to the ratio of R
In Figure 13 we use a THAT 1243 -3 dB line
Figure 10. Precision two-input summing circuit
Input 2
Input 1
2
3
In-
In+
+24 dBu In
In Lo
In Hi
9k
9k
2
to R
7
4
V
V
Tel: [phone]; Fax: [phone]; Web: www.thatcorp.com
CC
EE
THAT Corporation; 45 Sumner Street; Milford, MA 01757-1656; USA
3
. This circuit can accept
9k
9k
Sense
U1
1240
Vout
Ref
3
2
Figure 12. Circuit for audio ADCs with balanced inputs
Figure 13. Automated gain control of a balanced signal
In-
In+
5
6
1
Sense
1
Ref
Copyright © 2008, THAT Corporation
Output
5
Vout
THAT
1246
U2
2
3
6
In-
In+
Sense
Ref
1
Page 7 of 8
5
Vout
THAT
1246
U1
1
U3A
4570
+24 dBu
6
+24 dBu, since the THAT 1243 output stage is
capable of accepting 21 dBu without distortion.
Reducing R
VCA output noise. This arrangement results in 3 dB
greater dynamic range compared to the case where a
-6 dB line receiver and a VCA with zero dB static gain
are used. After the VCA, the signal is restored to 24
dBu by the THAT 1606.
3
2
2k10
2k10
R19
1/2 Vref of ADC
In+
R8
In-
R1
Rg
C4
6n8
Figure 11. Instrumentation amplifier
3
to 14 kΩ results in a 3 dB reduction in
6
5
3
2
4k99
4k99
R2
R3
U2A
OP-270B
U2B
OP-270B
R9
249R
7
1
AIN+ to ADC
AIN- to ADC
Zero dBu Out
100n
2
3
Balanced Line Receiver ICs
C1
100n
C2
In-
In+
V
V
V
CC
CC
V
EE
7
EE
4
Sens
Ref
THAT 1240 Series
1
5
Out
THAT1240
U1
6
Out