T H AT
Corporation
FEATURES
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OutSmarts脭 technology tames
clipping behavior into single-ended
loads
Pin-compatible with SSM2142
Balanced, floating output delivers
transformer-like behavior
Stable when driving long cables
and capacitive loads
THAT 1430 delivers low output
offset voltage using single capacitor
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OutSmarts盲
Balanced Line Drivers
THAT
1420, 1430
APPLICATIONS
Differential Line Driver
Audio Mix Consoles
Distribution Amplifiers
Audio Equalizers
Dynamic Range Processors
Digital Effects Processors
Telecommunications Systems
Instrumentation
Hi-Fi Equipment
Description
The THAT 1420 and 1430 are a new genera-
tion of audio differential line drivers with im-
proved
performance
over
conventional
cross-coupled monolithic designs. Both models
exhibit low noise and distortion, high slew rate,
stability under difficult loads, wide output swing,
and have outputs which are short-circuit pro-
tected.
In addition both models incorporate patented
OutSmarts脭 technology, a dual feedback-loop de-
sign that prevents the excessive ground currents
typical of cross-coupled output stages (CCOS)
when clipping into single-ended loads
1
.
To overcome this problem, the THAT 1420
and 1430 use two individual negative-feedback
loops to separately control the differential output
voltage and common mode output currents, mak-
ing the design inherently more stable and less
sensitive to component tolerances than the CCOS.
Most importantly, the dual-feedback design pre-
vents the loss of common-mode feedback that
plagues the CCOS designs, avoiding the excessive
ground currents and overly-distorted output
waveform that can result when driving sin-
gle-ended loads.
Where minimum output offset voltage with
minimum parts count is desired, the THAT 1430
further improves over existing designs. In con-
ventional CCOS circuits, two relatively high-value
electrolytic capacitors are required to reduce the
offset voltage. By contrast, the THAT 1430 topol-
ogy requires only a resistor and a single film or
ceramic capacitor to achieve the same effect at
lower parts count and price.
DIP Pin
Number
Out-
C
EXT
Sens+
5k
In+
Din+
Cin+
Cin-
Gnd
5k
Din-
10k
Dout-
10k
10p
20k
THAT 1420
10k
50
SO Pin
Number
3
4
5
6
11
12
13
14
1420 Pin
Name
Out-
Sens-
Gnd
In
Vee
Vcc
Sens+
Out+
1430 Pin
Name
Out-
Cap2
Gnd
In
Vee
Vcc
Cap1
Out+
Vcc
1
2
3
4
5
C
EXT
A
D
& A
C
Dout+
10k
10k
10k
20k
Sens-
Vee
50
Out+
6
7
8
Figure 1. THAT 1420 Equivalent Circuit Diagram
Table 1. THAT 1420/1430 pin assignments
1. See Gary Hebert鈥檚 paper, An Improved Balanced, Floating Output Driver IC, presented at the 108th AES Convention, Feb. 2000
THAT Corporation; 45 Sumner Street; Milford, Massachusetts 01757-1656; USA
Tel: +1 (508) 478-9200; Fax: +1 (508) 478-0990; Web: www.thatcorp.com
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