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)
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.
Peak-to-peak input voltage for each 30-dB stage0.011V
Operating free-air temperature, T
2
A
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
–55125°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 voltage1± 25± 70mV
Quiescent output voltage25.455.65.85V
DC scale factor (differential output), each 3-dB stage, – 35 dBV to – 5 dBV37811mV/dB
AC scale factor (differential output)8mV/dB
DC error at – 20 dBV (midpoint of – 35 dBV to – 5 dBV range)312.6dB
Input impedance500Ω
Output impedance200Ω
Rise time, 10% to 90% points, CL = 24 pF42035ns
Supply current from V
Supply current from VCC
Power dissipation2123162201mW
CC+
–
electrical characteristics over operating free-air temperature range, V
= ±6 V, TA = 25°C
CC±
PARAMETER
TEST
FIGURE
214.518.523mA
2– 6– 8.5– 10.5mA
MINTYPMAXUNIT
= ±6 V (unless otherwise
CC±
noted)
PARAMETER
Differential output offset voltage1± 100mV
Quiescent output voltage25.35.85V
DC scale factor (differential output) each 30-dB stage, – 35 dBV to – 5 dBV3711mV/dB
TA = – 55°C
TA = 125°C
CC+
p
– 35
–
– 5
– 20
Supply current from V
Supply current from VCC
Power dissipation287276mW
TEST
FIGURE
21031mA
2– 4.5– 15mA
MINMAXUNIT
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–
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
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
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
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 – 250255075100 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 – 250255075100 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 – 250255075100 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 – 250255075100 125
TA – Free-Air Temperature –°C
Figure 8
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
5
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