Texas Instruments TL441N Datasheet

TL441

LOGARITHMIC AMPLIFIER

SLVS328 – OCTOBER 2000

C

A2

CC –

C

A2′

A1

A2

CC +

Y
Y

N PACKAGE

(TOP VIEW)

16

1

15

2

14

3

13

4

12

5

11

6

10

7
8

9

NC
C

B2

C

B2′

GND
B1
Z
Z
B2

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 amplifier circuit contains four 30-dB
logarithmic stages. Gain in each stage is such that
the output of each stage is proportional to the

V

V

logarithm of the input voltage over the 30-dB input
voltage range. Each half of the circuit contains two

NC — No internal connection

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 typically to be 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 data compression and analog compensation. This logarithmic amplifier is used in log IF
circuitry as well as video and log amplifiers.

The TL441 is characterized for operation over 0°C to 70°C.

Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.

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.

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Copyright  2000, Texas Instruments Incorporated

1

TL441
LOGARITHMIC AMPLIFIER

SLVS328 – OCTOBER 2000

functional logic diagram (one half)

A1

(B1)

–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

, CB2, and C

A2′

are detector compensation inputs.

B2′

Log

Log

Log

Log

Σ

schematic

Y (Z)

Y

(Z)

VCC

C

C

V

CC –

A2

A1

A2′

A2

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

2

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TL441

LOGARITHMIC AMPLIFIER

SLVS328 – OCTOBER 2000

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. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Package thermal impedance, θ

Lead temperature 1,6 mm (1/16 inch) from case for 10 seconds 260°C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Storage temperature range, T

†

Stresses beyond those listed under “absolute maximum ratings” may cause permanent damage to the device. These are stress ratings only, and
functional operation of the device at these or any other conditions beyond those indicated under “recommended operating conditions” is not
implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.

NOTES: 1. All voltages, except differential out voltages, are with respect to network ground terminal.

2. Maximum power dissipation is a function of TJ(max),
ambient temperature is PD = (TJ(max) – TA)/

3. The package thermal impedance is calculated in accordance with JESD 51-7.

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

CC+

V

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

CC –

(see Notes 2 and 3) 67°C/W. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

JA

–65°C to 150°C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

stg

θ

, and TA. The maximum allowable power dissipation at any allowable

θ

JA

JA

. Operating at the absolute maximum TJ of 150°C can affect reliability.

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

electrical characteristics, V

Differential output offset voltage 1 ±40 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 6 8 12 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 dB
Input impedance 500 Ω
Output impedance 200 Ω
Rise time, 10% to 90% points, CL = 24 pF 4 20 30 ns
Supply current from V
Supply current from VCC
Power dissipation 2 123 162 201 mW

CC+

A

= ±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

0 70 °C

†

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3

TL441
LOGARITHMIC AMPLIFIER

SLVS328 – OCTOBER 2000

PARAMETER MEASUREMENT INFORMATION

V

CC+VCC–

CA2C

A2′VCC +VCC –

A1
A2
B1

B2

CB2C

B2′

GND

ICC

+

V

CC+

V

CC–

I

CC –

CA2C

A2′VCC+VCC–

Y
Y
Z
Z

DVM

A1
A2
B1

B2

CB2C

B2′

GND

Y
Y
Z
Z

V

O

Figure 1

PD = V

CC+

Figure 2

• I

CC+

+ V

CC–

• I

CC–

4

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TL441

LOGARITHMIC AMPLIFIER

SLVS328 – OCTOBER 2000

PARAMETER MEASUREMENT INFORMATION

V

CC+VCC–

CA2C

18 mV
100 mV
560 mV

DC

Power

Supply

A2′VCC+VCC–

A1
A2
B1

B2

C

B2

GND

C

B2′

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

Vout(100 mV)

+

30 dBV

–0.5 V

Figure 3

I

CA2C

A2′VCC+VCC–

A1
A2
B1

B2

CB2C

out(560 mV)

Scale Factor

V

CC+VCC–

GND

B2′

ƫ

mV

ƫ

1000 pFC

Tektronix

Sampling Scope

With Digital

Readout or

Equivalent

C

L

Y
Y
Z
Z

–0.5 V

C

L

out(18 mV)

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

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5