THAT Corporation; 45 Sumner Street; Milford, Massachusetts 01757-1656; USA

Tel: +1 (508) 478-9200; Fax: +1 (508) 478-0990; Web: www.thatcorp.com

THAT 1420, 1430

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

OutSmartsÔ technology, a dual feedback-loop de-

sign that prevents the excessive ground currents

typical of cross-coupled output stages (CCOS)

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.

OutSmartsä Balanced Line Drivers

FEATURES

·

OutSmartsÔ 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

APPLICATIONS

·

Differential Line Driver

·

Audio Mix Consoles

·

Distribution Amplifiers

·

Audio Equalizers

·

Dynamic Range Processors

·

Digital Effects Processors

·

Telecommunications Systems

·

Instrumentation

·

Hi-Fi Equipment

Din+

Cin+

Cin-

Din-

Out-

Sens+

Out+

Sens-

Vcc

In+

Vee

Gnd

Dout-

Dout+

10k

10k

50

5k

5k

10k

10k

10k

10k

20k

20k

10p

50

THAT 1420

D

C

AA

&

Figure 1. THAT 1420 Equivalent Circuit Diagram

1. See Gary Hebert’s paper, An Improved Balanced, Floating Output Driver IC, presented at the 108th AES Convention, Feb. 2000

DIP Pin

Number

SO Pin

Number

1420 Pin

Name

1430 Pin

Name

1

3

Out-

Out-

2

4

Sens-

Cap2

35

Gnd

Gnd

4

6

In

In

5

11

Vee

Vee

6

12

Vcc

Vcc

7

13

Sens+

Cap1

8

14

Out+

Out+

Table 1. THAT 1420/1430 pin assignments