TL441AM

LOGARITHMIC AMPLIFIER

SLFS038 – JUNE 1976 – REVISED FEBRUARY 1989

1

POST OFFICE BOX 655303

description

This monolithic amplifier circuit contains four

30-dB logarithmic stages. Gain in each stage is

such that the output of each stage is proportional

to the logarithm of the input voltage over the 30-dB

input voltage range. Each half of the circuit

contains two of these 30-dB stages summed

together

in

one

differential

output

that is

proportional to the sum of the logarithms of the

input voltages of the two stages. The four stages

may be interconnected to obtain a theoretical

input voltage range of 120-dB. In practice, this

permits the input voltage range to be typically

greater than 80-dB with log linearity of

± 0.5-dB

(see application data). Bandwidth is from dc to

40 MHz.

This circuit is useful in military weapons systems,

broadband radar, and infrared reconnaissance

systems. It serves for data compression and

analog compensation. This logarithmic amplifier

is used in log IF circuitry as well as video and log

amplifiers. The TL441AM is characterized for

operation over the full military temperature range

of – 55

°C to 125°C.

Copyright

© 1989, Texas Instruments Incorporated

PRODUCTION DATA information is current as of publication date.

Products conform to specifications per the terms of Texas Instruments

standard warranty. Production processing does not necessarily include

testing of all parameters.

1

2

3

4

5

6

7

8

16

15

14

13

12

11

10

9

A1

Y

Y

A2

NC

GND

B1

Z

Z

B2

J PACKAGE

(TOP VIEW)

3

2

1 20 19

910 11 12 13

4

5

6

7

8

18

17

16

15

14

GND

NC

B1

Z

A1

NC

Y

Y

FK PACKAGE

(TOP VIEW)

NC — No internal connection

–15 dB

–15 dB

Log

Log

Log

Log

Σ

Y (Z)

Y (Z)

A1

(B1)

CA2

(CB2)

CA2

′

(CB2

′)

Y

∝ log A1 + log A2; Z ∝ log B1 + log B2

where: A1, A2, B1, and B2 are in dBV, 0 dBV = 1 V.

CA2, CA2

′, CB2, and CB2′ are detector compensation inputs.

A2

(B2)

functional block diagram (one half)