LOG100

Precision

LOGARITHMIC AND LOG RATIO AMPLIFIER

resistors. The resistors are laser-trimmed for maxi-

mum precision. FET input transistors are used for the

amplifiers whose low bias currents (1pA typical) per-

mit signal currents as low as 1nA while maintaining

guaranteed total errors of 0.37% FSO maximum.

Because scaling resistors are self-contained, scale

factors of 1V, 3V or 5V per decade are obtained

simply by pin selections. No other resistors are re-

quired for log ratio applications. The LOG100 will

meet its guaranteed accuracy with no user trimming.

Provisions are made for simple adjustments of scale

factor, offset voltage, and bias current if enhanced

performance is desired.

DESCRIPTION

The LOG100 uses advanced integrated circuit tech-

nologies to achieve high accuracy, ease of use, low

cost, and small size. It is the logical choice for your

logarithmic-type computations. The amplifier has guar-

anteed maximum error specifications over the full six-

decade input range (1nA to 1mA) and for all possible

combinations of I

that involved error computations are not necessary.

The circuit uses a specially designed compatible thin-

film monolithic integrated circuit which contains am-

plifiers, logging transistors, and low drift thin-film

PDS-437E

FEATURES

q ACCURACY

0.37% FSO max Total Error

Over 5 Decades

q LINEARITY

0.1% max Log Conformity

Over 5 Decades

q EASY TO USE

Pin-selectable Gains

Internal Laser-trimmed Resistors

q WIDE INPUT DYNAMIC RANGE

6 Decades, 1nA to 1mA

q HERMETIC CERAMIC DIP

APPLICATIONS

q LOG, LOG RATIO AND ANTILOG

COMPUTATIONS

q ABSORBANCE MEASUREMENTS

q DATA COMPRESSION

q OPTICAL DENSITY MEASUREMENTS

q DATA LINEARIZATION

q CURRENT AND VOLTAGE INPUTS

®

International Airport Industrial Park

•

Mailing Address: PO Box 11400

•

Tucson, AZ 85734

• Street Address: 6730 S. Tucson Blvd.

•

Tucson, AZ 85706

Tel: (520) 746-1111

•

Twx: 910-952-1111

•

Cable: BBRCORP

•

Telex: 066-6491

•

FAX: (520) 889-1510

•

Immediate Product Info: (800) 548-6132

7

A

2

A

1

1

14

I

1

9

–V

CC

6

+V

CC

10

Com

I

2

Q

1

Q

2

V

OUT

3

K = 1

4

K = 3

5

K = 5

2

Scale

Factor

Trim

39k

Ω

24k

Ω

7.5k

Ω

270

Ω

220

Ω

Resistor values nominal only;

laser-trimmed for precision gain.

V

I

1

I

2

© 1981 Burr-Brown Corporation

PDS-437E

Printed in U.S.A. January, 1995