LOG100 Datasheet, PDF (1/9 Pages) Burr-Brown (TI) – Precision LOGARITHMIC AND LOG RATIO AMPLIFIER

®
LOG100
Precision
LOGARITHMIC AND LOG RATIO AMPLIFIER
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
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 I₁ and I₂. Total error is guaranteed so
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
9
–V_CC
1
I₁
Q₁
Q₂
A₁
14
I₂
6
+V_CC
10
Com
V_OUT = K LOG
I₁
I₂
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
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.
A₂
270Ω
220Ω
7.5kΩ
24kΩ
7
V_OUT
3
K=1
4
K=3
5
K=5
39kΩ
Scale
Factor
2 _Trim
Resistor values nominal only;
laser-trimmed for precision gain.
International Airport Industrial Park • Mailing Address: PO Box 11400 • Tucson, AZ 85734 • Street Address: 6730 S. Tucson Blvd. • Tucson, AZ 85706
Tel: [phone] • Twx: 910-952-1111 • Cable: BBRCORP • Telex: 066-6491 • FAX: [phone] • Immediate Product Info: [phone]
© 1981 Burr-Brown Corporation
PDS-437E
Printed in U.S.A. January, 1995