Applications
RFI Protection
Figure 3 shows the THAT 1200 configured with
robust RFI input protection.
In applications where
RFI rejection is of less concern, the circuit shown Fig-
ure 4 provides a less aggressive approach.
Bootstrap coupling capacitor
Referring to Figure 3, electrolytic capacitor Cb
provides the feedback path for the boostrap circuit.
The capacitor value is chosen to be high enough to
present a sufficiently small impedance to signals at
the low end of the audio spectrum. Its voltage rating
is dependent on the topology of the surrounding cir-
cuitry, as described in the following paragraphs.
AC signals presented to the input stage cause the
two ends of capacitor Cb to swing in tandem so that
virtually no voltage appears across the capacitor.
Consequently, capacitors with small DC working volt-
ages may be used when the previous stage is AC cou-
pled to the input of the THAT 1200.
THAT Corporation; 45 Sumner Street; Milford, Massachusetts 01757-1656; USA
Tel: +1 (508) 478-9200; Fax: +1 (508) 478-0990; Web: www.thatcorp.com
Page 4
InGenius Balanced Line Receiver
Preliminary Information
Electrical Characteristics (Cont’d)
Parameter
Symbol
Conditions
Min
Typ
Max
Units
Output Short Circuit Current
ISC
RL =RLcm =0 W
—
±25
—
mA
ICMSC
At CM output
—
±10
—
mA
Minimum Resistive Load
RLmin
2—
—
k
W
RLCMmin
At CM output
10
—
—
k
W
Maximum Capacitive Load
CLmax
—
—
300
pF
CLCMmax
At CM output
—
—
50
pF
1
In-
2
In+
3
CMin
5
4
8
7
Out
6
U1
THAT120x
Cb
100u
C1
56p
C2
300p
C3
100n
C4
100n
R1
200k
R2
200k
R3
600R
R4
2k
R5
100R
R6
100R
Vcc
Vee
In-
In+
Ext. DC Source
CM Out
Main Out
Gnd
Gnd
Gnd
CMout
Vcc
Ref
Vee
Figure 2. THAT1200-series test circuit
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