Datasheet TL441AMJ, TL441AMFK Datasheet (Texas Instruments)

TL441AM

LOGARITHMIC AMPLIFIER

SLFS038 – JUNE 1976 – REVISED FEBRUARY 1989

D

Excellent Dynamic Range

D

Wide Bandwidth

D

Built-In Temperature Compensation

D

Log Linearity (30 dB Sections) ...1 dB Typ

D

Wide Input Voltage Range

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.

J PACKAGE
(TOP VIEW)

NC

NC

16
15
14
13
12
11
10

9

NC

B2

NC
C
C
GND
B1
Z
Z
B2

B2

C

18
17
16
15
14

Z

B2
B2′

C
GND
NC
B1
Z

C

1

A2

V

V

C

A2′

A1

NC

Y
Y

2

CC –

C

3

A2′

A1

4

Y

5

Y

6

A2

7
8

CC +

FK PACKAGE

(TOP VIEW)

CC –

V

3 2 1 20 19

4
5
6
7
8

910111213

C

A2

A2

CC +

V

NC — No internal connection

functional block diagram (one half)

A1

(B1)

Log

Σ

B2′

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.

–15 dB

C

A2

(CB2)

A2

(B2)

–15 dB

C

A2′

(C

)

B2′

Y ∝ log A1 + log A2; Z ∝ log B1 + log B2
where: A1, A2, B1, and B2 are in dBV, 0 dBV = 1 V.
CA2, C

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

, CB2, and C

A2′

Log

Log

Log

are detector compensation inputs.

B2′

Copyright  1989, Texas Instruments Incorporated

Y (Z)

(Z)

Y

1

TL441AM
LOGARITHMIC AMPLIFIER

SLFS038 – JUNE 1976 – REVISED FEBRUARY 1989

schematic

A2

A1

C

A2′

C

A2

CC –

8

+

6

Y

5

Y

7

4

3
1

2

10
11

12

13

14
15

Z
Z

9

B2

B1

GND

C

B2′

C

B2

VCC

V

Pin numbers shown are for the J package.

absolute maximum ratings over operating free-air temperature range (unless otherwise noted)

Supply voltages (see Note 1): V

Input voltage (see Note 1) 6 V. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Output sink current (any one output) 30 mA. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Continuous total dissipation See Dissipation Rating Table. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Operating free-air temperature range –55°C to 125°C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Storage temperature range –65°C to 150°C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Case temperature for 60 seconds: FK package 260°C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Lead temperature 1,6 mm (1/16 inch) from case for 60 seconds: J package 300°C. . . . . . . . . . . . . . . . . . . . .

†

Stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. This is a stress rating only, and
functional operation of the device at these or any other conditions beyond those indicated in the recommended operating conditions section of this
specification is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.

NOTE 1: All voltages, except differential output voltages, are with respect to network ground terminal.

8 V. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

CC+

V

–8 V. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

CC –

†

DISSIPATION RATING TABLE

PACKAGE

FK 500 mW 11.0 mW/°C 104°C 500 mW 275 mW

J 500 mW 11.0 mW/°C 104°C 500 mW 275 mW

TA ≤ 25°C

POWER RATING

DERATING

FACTOR

DERATE

ABOVE T

TA = 70°C

A

POWER RATING

TA = 125°C

POWER RATING

recommended operating conditions

MIN MAX UNIT

Peak-to-peak input voltage for each 30-dB stage 0.01 1 V
Operating free-air temperature, T

2

A

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

–55 125 °C

DC error at

dBV (midpoint of

dBV to

dBV range)

33dB

TL441AM

LOGARITHMIC AMPLIFIER

SLFS038 – JUNE 1976 – REVISED FEBRUARY 1989

electrical characteristics, V

Differential output offset voltage 1 ± 25 ± 70 mV
Quiescent output voltage 2 5.45 5.6 5.85 V
DC scale factor (differential output), each 3-dB stage, – 35 dBV to – 5 dBV 3 7 8 11 mV/dB
AC scale factor (differential output) 8 mV/dB
DC error at – 20 dBV (midpoint of – 35 dBV to – 5 dBV range) 3 1 2.6 dB
Input impedance 500 Ω
Output impedance 200 Ω
Rise time, 10% to 90% points, CL = 24 pF 4 20 35 ns
Supply current from V
Supply current from VCC
Power dissipation 2 123 162 201 mW

CC+

–

electrical characteristics over operating free-air temperature range, V

= ±6 V, TA = 25°C

CC±

PARAMETER

TEST

FIGURE

2 14.5 18.5 23 mA
2 – 6 – 8.5 – 10.5 mA

MIN TYP MAX UNIT

= ±6 V (unless otherwise

CC±

noted)

PARAMETER

Differential output offset voltage 1 ± 100 mV
Quiescent output voltage 2 5.3 5.85 V
DC scale factor (differential output) each 30-dB stage, – 35 dBV to – 5 dBV 3 7 11 mV/dB

TA = – 55°C
TA = 125°C

CC+

p

– 35

–

– 5

– 20

Supply current from V
Supply current from VCC
Power dissipation 2 87 276 mW

TEST

FIGURE

2 10 31 mA
2 – 4.5 – 15 mA

MIN MAX UNIT

4

CA2C

A2′VCC +VCC –

A1
A2
B1

B2

CB2C

Figure 1

PARAMETER MEASUREMENT INFORMATION

V

CC+VCC–

CA2C

A2′VCC+VCC–

A1
A2
B1

B2

CB2C

PD = V

B2′

GND

Y
Y
Z
Z

DVM

B2′

CC+

Figure 2

GND

• I

CC+

Y
Y
Z
Z

+ V

CC–

• I

CC–

ICC

I

CC –

V

O

+

V

CC+

V

CC–

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3

TL441AM
LOGARITHMIC AMPLIFIER

SLFS038 – JUNE 1976 – REVISED FEBRUARY 1989

PARAMETER MEASUREMENT INFORMATION

18 mV
100 mV
560 mV

DC

Power

Supply

CA2C

A2′VCC+VCC–

A1
A2
B1

B2

C

B2

V

CC+VCC–

C

B2′

GND

Y
Y
Z
Z

DVM

Pulse

Generator

50 Ω

Scale Factor

Error

Atten

100 mV
0 mV

ƪ

V

out(560 mV)–Vout(18mV)

+

ƪ

+

V

V

out(100 mV)

30 dB

Figure 3

I

CA2C

A1
A2
B1

B2

CB2C

A2′VCC+VCC–

–0.5 V

out(560 mV)

Scale Factor

V

CC+VCC–

GND

B2′

ƫ

mV

–0.5 V

out(18 mV)

1000 pFC

Y
Y
Z
Z

C

L

ƫ

Sampling Scope

C

L

Tektronix

With Digital

Readout or

Equivalent

NOTES: A. The input pulse has the following characteristics: tw = 200 ns, tr ≤ 2 ns, tf ≤ 2 ns, PRR ≤ 10 MHz.

B. Capacitor CI consists of three capacitors in parallel: 1 µF, 0.1 µF, and 0.01 µF.

C. CL includes probe and jig capacitance.

Figure 4

4

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TL441AM

LOGARITHMIC AMPLIFIER

SLFS038 – JUNE 1976 – REVISED FEBRUARY 1989

TYPICAL CHARACTERISTICS

DIFFERENTIAL OUTPUT OFFSET VOLTAGE

vs

FREE-AIR TEMPERATURE

60

50

40

30

20

10

V

= ±6 V

Differential Output Offset Voltage – mV

CC±

See Figure 1

0

– 75 – 50 – 25 0 25 50 75 100 125

TA – Free-Air Temperature –°C

Figure 5

DC SCALE FACTOR

vs

FREE-AIR TEMPERATURE

12

QUIESCENT OUTPUT VOLTAGE

vs

FREE-AIR TEMPERATURE

8

7

6

5

4

3

2

Quiescent Output Voltage – V

V

= ±6 V

1

0

CC±

See Figure 2

– 75 – 50 – 25 0 25 50 75 100 125

TA – Free-Air Temperature –°C

Figure 6

DC ERROR

vs

FREE-AIR TEMPERATURE

2.0

10

8

6

4

2

V

= ±6 V

CC±

See Figure 3

0

DC Scale Factor (Differential Output) – mV/dBV

– 75 – 50 – 25 0 25 50 75 100 125

TA – Free-Air Temperature –°C

Figure 7

1.8

1.6

1.4

1.2

1.0

0.8

0.6

0.4
V

= ±6 V

0.2

DC Error at Midpoint of 30-dBV Range – dBV

0

CC±

See Figure 3

– 75 – 50 – 25 0 25 50 75 100 125

TA – Free-Air Temperature –°C

Figure 8

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5

TL441AM
LOGARITHMIC AMPLIFIER

SLFS038 – JUNE 1976 – REVISED FEBRUARY 1989

– Output Rise Time – ns

r

t

TYPICAL CHARACTERISTICS

OUTPUT RISE TIME

vs

LOAD CAPACITANCE

25

20

15

10

V

= ±6 V

CC±

TA = 25°C
See Figure 4, outputs

5

loaded symmetrically

0

0 5 10 15 20 25 30

CL – Load Capacitance – pF

Figure 9

POWER DISSIPATION

vs

FREE-AIR TEMPERATURE

200
180
160
140
120
100

80
60

Power Dissipation – mW

V

40
20

0
– 75 – 50 – 25 0 25 50 75 100 125

= ±6 V

CC±

See Figure 3

TA – Free-Air Temperature – °C

Figure 10

6

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

LOGARITHMIC AMPLIFIER

SLFS038 – JUNE 1976 – REVISED FEBRUARY 1989

APPLICATION INFORMATION

Although designed for high-performance applications such as broadband radar, infrared detection and
weapons systems, this device has a wide range of applications in data compression and analog computation.

TL441AM

basic logarithmic function

functional block diagram

The basic logarithmic response is derived from
the exponential current-voltage relationship of
collector current and base-emitter voltage. This
relationship is given in the equation:

m • V

= In [(IC + I

BE

CES

)/I

CES

]

where:

= collector current

I

C

I

= collector current at VBE = 0

CES

m = q/kT (in V

= base-emitter voltage

V

BE

– 1

)

The differential input amplifier allows dual-polarity
inputs, is self-compensating for temperature
variations, and is relatively insensitive to
common-mode noise.

INPUT

C

INPUT

C

A1

A2’

Log

–15 dB

Log

A2

A2

–15 dB

Log

Log

ΣΣ

YY

Outputs

Log

–15 dB

Log

Log

–15 dB

Log

ZZ

Figure 11

logarithmic sections

As can be seen from the schematic, there are eight differential pairs. Each pair is a 15-dB log subsection, and
each input feeds two pairs for a range of 30-dB per stage.

INPUT
B1

C

B2

INPUT
B2

C

B2’

Four compensation points are made available to allow slight variations in the gain (slope) of the two individual
15-dB stages of input A2 and B2. By slightly changing the voltage on any of the compensation pins from its
quiescent value, the gain of that particular 15-dB stage can be adjusted to match the other 15-dB stage in the
pair. The compensation pins may also be used to match the transfer characteristics of input A2 to A1 or B2 to
B1.

The log stages in each half of the circuit are summed by directly connecting their collectors together and
summing through a common-base output stage. The two sets of output collectors are used to give two log
outputs, Y and Y

(or Z and Z) which are equal in amplitude but opposite in polarity . This increases the versatility

of the device.
By proper choice of external connections, linear amplification, and linear attenuation, and many different

applications requiring logarithmic signal processing are possible

input levels

The recommended input voltage range of any one stage is given as 0.01 V to 1 V. Input levels in excess of
1 V may result in a distorted output. When several log sections are summed together, the distorted area of one
section overlaps with the next section and the resulting distortion is insignificant. However, there is a limit to the
amount of overdrive that may be applied. As the input drive reaches ±3.5 V, saturation occurs, clamping the
collector-summing line and severely distorting the output. Therefore, the signal to any input must be limited to
approximately ±3 V to ensure a clean output.

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7

TL441AM
LOGARITHMIC AMPLIFIER

SLFS038 – JUNE 1976 – REVISED FEBRUARY 1989

APPLICATION INFORMATION

output levels

Differential-output-voltage levels are low, generally less than 0.6 V. As demonstrated in Figure 12, the output
swing and the slope of the output response can be adjusted by varying the gain by means of the slope control.
The coordinate origin may also be adjusted by positioning the offset of the output buffer.

circuits

Figures 12 through 19 show typical circuits using this logarithmic amplifier. Operational amplifiers not otherwise
designated are TLC271. For operation at higher frequencies, the TL592 is recommended instead of the
TLC271.

TYPICAL TRANSFER

CHARACTERISTICS

1.4

1.2
Adjusted for Increased

1.0

Slope and Offset

Input

0.8

0.6

0.4

Output Voltage – V

0.2

0

– 0.2

10 – 410

–

+

A1

A2

Adjusted For Minimum
Slope With Zero Offset

–3

1/2

TL441

GND

–2

10

Input Voltage – V

Y

Y

–1

10

Origin

1

1

10

+
–

Output

Slope

Figure 12. Output Slope and Origin Adjustment

8

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TL441AM

LOGARITHMIC AMPLIFIER

SLFS038 – JUNE 1976 – REVISED FEBRUARY 1989

APPLICATION INFORMATION

TRANSFER CHARACTERISTICS

OF TWO TYPICAL INPUT STAGES

0.4

0.3

0.2

Output Voltage – V

0.1

Input

B1

B2

0

0.001

1/2

TL441

GND

0.01

Z

Z

0.1

Input Voltage – V

2 kΩ, 1% 2 kΩ, 1%

20 kΩ

2 kΩ, 1%

1

+
–

2 kΩ, 1%

Figure 13. Utilization of Separate Stages

10

Output

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9

TL441AM
LOGARITHMIC AMPLIFIER

SLFS038 – JUNE 1976 – REVISED FEBRUARY 1989

0.4

0.3

0.2

Output Voltage – V

0.1

APPLICATION INFORMATION

TRANSFER CHARACTERISTICS

WITH BOTH SIDES PARALLELED

Input

A1

A2

B1

B2

0

0.001

TL441

GND

0.01

Y

Y

Z

Z

0.1

Input Voltage – V

2 kΩ, 1% 2 kΩ, 1%

20 kΩ

2 kΩ, 1%

1

2 kΩ, 1%

Figure 14. Utilization of Paralleled Inputs

10

+
–

Output

10

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TL441AM

LOGARITHMIC AMPLIFIER

SLFS038 – JUNE 1976 – REVISED FEBRUARY 1989

APPLICATION INFORMATION

TRANSFER CHARACTERISTICS

0.8

0.7

0.6

0.5

0.4

0.3

Output Voltage – V

0.2

0.1

Input

1 kΩ

910 Ω

100 Ω

5 kΩ

1 kΩ

910 Ω

100 Ω

0

10 – 410

VCC + = 4 V

+
–

VCC – = – 4 V

VCC + = 4 V

+
–

VCC – = – 4 V

15 kΩ

–3

10

Input Voltage – V

5 kΩ

–2

A1

A2

B1

B2

10

TL441

–1

1

1

Y

Y

Z

Z

10

2 kΩ 2 kΩ

Origin

20 kΩ

2 kΩ

+
–

Slope

5 kΩ

Output

NOTES: A. Inputs are limited by reducing the supply voltages for the input amplifiers to ±4 V.

B. The gains of the input amplifiers are adjusted to achieve smooth transitions.

Figure 15. Logarithmic Amplifier With Input Voltage Range Greater Than 80 dB

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11

TL441AM
LOGARITHMIC AMPLIFIER

SLFS038 – JUNE 1976 – REVISED FEBRUARY 1989

RRRR

Input

A

Input

B

A1
+
–

+
–

A2

B1

B2

Y

TL441

Y

see

Note A

Z

Z

R

APPLICATION INFORMATION

R

+
+
–

R

RR

–

R

A1

+
–

A2

1/2

TL441

Y
Y

OUTPUT W
(see Note B)

NOTES: A. Connections shown are for multiplication. For division, Z and Z connections are reversed.

Multiplication: W = A • B ⇒ log W = log A + log B, or W = a
Division: W = A/B ⇒ log W = log A – log B, or W = a

B. Output W may need to be amplified to give actual product or quotient of A and B.
C. R designates resistors of equal value, typically 2 kΩ to 10 kΩ.

(logaA + logaB)

(logaA + logaB)

Figure 16. Multiplication or Division

RRRnR

A1

Input

A

NOTE: R designates resistors of equal value, typically 2 kΩ to 10 kΩ. The power to which the input variable is raised is fixed by setting nR.

Output W may need to be amplified to give the correct value.

Exponential: W = An ⇒ log W = n log A, or W = a(n

+
–

A2

1/2

TL441

Y

–

R

Y

+

nR

loga A)

–
+

R

R

+
–

B1
B2

TL441

1/2

Z
Z

Output

W

12

Figure 17. Raising a Variable to a Fixed Power

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TL441AM

LOGARITHMIC AMPLIFIER

SLFS038 – JUNE 1976 – REVISED FEBRUARY 1989

APPLICATION INFORMATION

2 kΩ 2 kΩ

Input

1

50 Ω

Input

2

50 Ω 50 Ω

Input

A

NOTE: Adjust the slope to correspond to the base “a”.

Origin

20 kΩ

Exponential to any base: W = a.

–

+

2 kΩ

2 kΩ

Slope

Figure 18. Raising a Fixed Number to a Variable Power

A1

TL592

50 Ω

TL592

+
–

Open

Gain Adj. = 400 Ω

For 30 dB

+
–

Open

0.2 µF

0.2 µF

A2

B1
B2

CA2C

10
kΩ

TL441

A2’

CB2C

10
kΩ

B2’

A1

+
–

Y

Y

Z

Z

2.2 kΩ
20 kΩ

2.2 kΩ

2.2 kΩ

20 kΩ

2.2 kΩ

A2

TL441

1/2

TL592

+

+

–

–

TL592

+

+

–

–

Y
Y

Output

Gain Adj.

Gain Adj.

W

0.2 µF

0.2 µF

1 kΩ 1 kΩ

0.2 µF

0.2 µF

1 kΩ 1 kΩ

Output

Output

1

2

Gain Adj. = 400 Ω

For 30 dB

VCC

–

Figure 19. Dual-Channel RF Logarithmic Amplifier With 50-dB Input Range Per Channel at 10 MHz

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pertaining to warranty, patent infringement, and limitation of liability.

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accordance with TI’s standard warranty. Testing and other quality control techniques are utilized to the extent
TI deems necessary to support this warranty . Specific testing of all parameters of each device is not necessarily
performed, except those mandated by government requirements.

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Copyright  1998, Texas Instruments Incorporated