1203P08-U THAT Corporation, 1203P08-U Datasheet - Page 9

• Manufacturer Part Number: 1203P08-U
• Description: Difference Amplifiers High-CMRR Bal Input Line Rec. -3dB DIP-8
• Manufacturer: THAT Corporation

Specifications of 1203P08-U

• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: 0 C
• Mounting Style: Through Hole
• Operating Temperature Range: 0 C to + 85 C
• Output Current: +/- 25 mA
• Operating Supply Voltage: +/- 18 V
• Package / Case: DIP-8
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

600033 Rev 00
will reduce the common-mode input impedance of
the 1200 stage to ~ 80 kΩ at 20 kHz. Of course, this
figure drops by a factor of ten for each decade in-
crease in frequency. Additionally, any mismatch be-
tween these capacitors can unbalance an interfering
common-mode signal, thus making it impossible for
the 1200 to reject it.
cuit for RFI protection. While more complex, it offers
many improvements over the circuit of Figure 10 that
make it worth serious consideration. First, C
are larger than their counterparts in Figure 10. Be-
cause they are in series with each other, they act as a
235 pf capacitor across pins 2 and 3 of the XLR.
This allows them to be effective at lower frequencies.
Second, because their center point ties to chassis
ground through a smaller, common capacitor (C
100 pf), any mismatch in their values has less ten-
dency to unbalance common-mode signals compared
to the circuit of figure 10
driven from the common-mode bootstrap circuit
through R
the InGenius common-mode bootstrapping. Finally,
R
ance against which the bypass capacitors can work,
making the entire network more effective against
strong RF signals.
ESD Protection
over-voltage protection circuitry for the two input
pins. Figure 12 is an equivalent circuit of this cir-
cuitry.
against common low-voltage ESD incidents.
ever, because these ICs are intended to be connected
directly
4
For additional information refer to the publications listed on page 7.
1
and R
The one drawback to this circuit is that C
Figure 11 shows a more elaborate and robust cir-
All
These internal diodes provide modest protection
the
2
to
3
, this common point gains the benefit of
provide some additional buildout imped-
5 4 3 1
the
2
1200-series
2
3
1
input
THAT Corporation; 45 Sumner Street; Milford, Massachusetts 01757-1656; USA
Tel: [phone]; Fax: [phone]; Web: www.thatcorp.com
J1
XLR-F
4
connectors
. Third, because they are
Figure 11. THAT1200 application with recommended RFI protection.
ICs
100R
100R
R2
R1
contain
of
470pF
C1
470pF
C2
electronic
1
1
internal
and C
and C
How-
C3
100pF
3
2
2
,
4k7
R3
products, they may be exposed to unpredictable and
possibly extreme ESD.
InGenius operation, it would have to be conducted
via one of the input connectors to the device itself.
This is unlikely, but certainly not impossible. Not
surprisingly, THAT's own testing indicates that re-
peated exposure to high levels (above 1 kV) of ESD
through pins 2 and/or 3 of the input XLR connector
can adversely affect the device's CMRR, and may
cause failure if the ESD reaches sufficiently high lev-
els.
cidents, THAT recommends the circuit of either Fig-
ure 13 or 14. Figure 13 is appropriate for the 1203
and 1206, both of which support input signals that
swing higher than the supply rails. This arrangement
of signal and Zener diodes permits the maximum al-
lowable (audio) input signal to reach the IC's input
If the application requires surviving such ESD in-
(see text)
220uF
Figure 12. Internal input protection circuitry
C b
IN+
2
5
3
IN-
+
CM
IN+
IN-
IN
1
8
120X
REF
OUT
CM
Vcc
Vee
Vcc
Vee
7
4
Vcc
Vcc
Vee
Vee
OUT
Ra
Rb
100nF
U1
100nF
C5
C4
For ESD to affect the
6
Rc
Rd
OUT
CM IN
Page 9