TL441AM LOGARITHMIC AMPLIFIER SLFS038 – JUNE 1976 – REVISED FEBRUARY 1989 J PACKAGE (TOP VIEW) Excellent Dynamic Range Wide Bandwidth Built-In Temperature Compensation Log Linearity (30 dB Sections) . . . 1 dB Typ Wide Input Voltage Range CA2 VCC – CA2′ A1 Y Y A2 VCC + 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. 16 2 15 3 14 4 13 5 12 6 11 7 10 8 9 NC CB2 CB2′ GND B1 Z Z B2 VCC – C A2 NC NC C B2 FK PACKAGE (TOP VIEW) CA2′ A1 NC Y Y 4 3 2 1 20 19 18 5 17 6 16 7 15 8 14 9 10 11 12 13 A2 V CC + NC B2 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. 1 CB2′ GND NC B1 Z Z D D D D D NC — No internal connection functional block diagram (one half) A1 (B1) Log Σ –15 dB Log Y (Z) Log Y (Z) CA2 (CB2) A2 (B2) –15 dB Log 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. 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. POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 1 TL441AM LOGARITHMIC AMPLIFIER SLFS038 – JUNE 1976 – REVISED FEBRUARY 1989 schematic VCC + Y Y A2 A1 8 6 10 5 11 7 9 4 12 13 CA2′ CA2 VCC – 3 14 1 15 Z Z B2 B1 GND CB2′ CB2 2 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): VCC+ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 V VCC – . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . – 8 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. DISSIPATION RATING TABLE PACKAGE TA ≤ 25°C POWER RATING DERATING FACTOR DERATE ABOVE TA TA = 70°C POWER RATING TA = 125°C POWER RATING 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 recommended operating conditions MIN MAX UNIT Peak-to-peak input voltage for each 30-dB stage 0.01 1 V Operating free-air temperature, TA – 55 125 °C 2 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 TL441AM LOGARITHMIC AMPLIFIER SLFS038 – JUNE 1976 – REVISED FEBRUARY 1989 electrical characteristics, VCC± = ±6 V, TA = 25°C TEST FIGURE PARAMETER MIN TYP MAX UNIT 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 AC scale factor (differential output) mV/dB 8 DC error at – 20 dBV (midpoint of – 35 dBV to – 5 dBV range) 3 mV/dB 1 2.6 dB Input impedance 500 Ω Output impedance 200 Ω Rise time, 10% to 90% points, CL = 24 pF 4 Supply current from VCC+ 2 20 35 ns 14.5 18.5 23 mA Supply current from VCC – Power dissipation 2 –6 – 8.5 – 10.5 mA 2 123 162 201 mW electrical characteristics over operating free-air temperature range, VCC ± = ±6 V (unless otherwise noted) TEST FIGURE PARAMETER MIN MAX UNIT Differential output offset voltage 1 ± 100 mV Quiescent output voltage 2 5.3 5.85 V 3 7 11 DC scale factor (differential output) each 30-dB stage, – 35 dBV to – 5 dBV DC error at – 20 dBV (midpoint of – 35 dBV to – 5 dBV range) TA = – 55°C TA = 125°C mV/dB 4 3 3 dB Supply current from VCC+ 2 10 31 mA Supply current from VCC – 2 – 4.5 – 15 mA Power dissipation 2 87 276 mW PARAMETER MEASUREMENT INFORMATION VCC+ ICC + VCC– VCC+ VCC– ICC – CA2 CA2′ VCC+ VCC– Y A1 CA2 CA2′ VCC + VCC – Y A1 A2 B1 Y B2 Z DVM Z Y A2 B1 Z B2 Z CB2 CB2′ GND CB2 CB2′ GND VO PD = VCC+ Figure 1 • ICC+ + VCC– • ICC– Figure 2 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 3 TL441AM LOGARITHMIC AMPLIFIER SLFS038 – JUNE 1976 – REVISED FEBRUARY 1989 PARAMETER MEASUREMENT INFORMATION VCC+ VCC– CA2 CA2′ VCC+ VCC– Y A1 Y A2 B1 Z B2 18 mV 100 mV 560 mV Error ƪ ƪ + + V Z CB2 CB2′ GND DC Power Supply Scale Factor DVM ƫ –V mV out(560 mV) out(18mV) 30 dB VV out(100 mV)–0.5 V out(560 mV)–0.5 V out(18 mV) Scale Factor ƫ Figure 3 VCC+ CI Atten 100 mV 0 mV Pulse Generator 50 Ω VCC– 1000 pF CA2 CA2′ VCC+ VCC– Y A1 Y A2 B1 Z B2 Tektronix Sampling Scope With Digital Readout or Equivalent Z CB2 CB2′ GND CL CL 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 QUIESCENT OUTPUT VOLTAGE vs FREE-AIR TEMPERATURE DIFFERENTIAL OUTPUT OFFSET VOLTAGE vs FREE-AIR TEMPERATURE 8 7 50 Quiescent Output Voltage – V Differential Output Offset Voltage – mV 60 40 30 20 10 VCC ± = ± 6 V See Figure 1 0 – 75 – 50 – 25 6 5 4 3 2 1 0 25 50 75 100 VCC ± = ± 6 V See Figure 2 0 – 75 – 50 – 25 125 Figure 5 DC Error at Midpoint of 30-dBV Range – dBV DC Scale Factor (Differential Output) – mV/dBV 10 8 6 4 VCC ± = ± 6 V See Figure 3 25 75 100 125 DC ERROR vs FREE-AIR TEMPERATURE 12 0 50 Figure 6 DC SCALE FACTOR vs FREE-AIR TEMPERATURE 0 – 75 – 50 – 25 25 TA – Free-Air Temperature – °C TA – Free-Air Temperature – °C 2 0 50 75 100 125 2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 VCC ± = ± 6 V See Figure 3 0 – 75 – 50 – 25 TA – Free-Air Temperature – °C 0 25 50 75 100 125 TA – Free-Air Temperature – °C Figure 7 Figure 8 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 5 TL441AM LOGARITHMIC AMPLIFIER SLFS038 – JUNE 1976 – REVISED FEBRUARY 1989 TYPICAL CHARACTERISTICS OUTPUT RISE TIME vs LOAD CAPACITANCE t r – Output Rise Time – ns 25 20 15 10 VCC ± = ± 6 V TA = 25°C See Figure 4, outputs loaded symmetrically 5 0 0 5 10 15 20 25 CL – Load Capacitance – pF 30 Figure 9 POWER DISSIPATION vs FREE-AIR TEMPERATURE 200 Power Dissipation – mW 180 160 140 120 100 80 60 40 VCC ± = ± 6 V See Figure 3 20 0 – 75 – 50 – 25 0 25 50 75 100 TA – Free-Air Temperature – °C Figure 10 6 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 125 TL441AM 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. 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: INPUT A1 Log –15 dB m • VBE = In [(IC + ICES)/ICES] where: INPUT B1 Log –15 dB Log Log CB2 CA2 IC = ICES = m = VBE = INPUT A2 collector current collector current at VBE = 0 Log –15 dB q/kT (in V – 1) –15 dB Log base-emitter voltage Log Σ CA2’ The differential input amplifier allows dual-polarity inputs, is self-compensating for temperature variations, and is relatively insensitive to common-mode noise. INPUT B2 Log Y Σ Y Z CB2’ Z Outputs 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. 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. POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 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 Output Voltage – V 1.0 Adjusted for Increased Slope and Offset 0.8 0.6 0.4 0.2 Adjusted For Minimum Slope With Zero Offset 0 – 0.2 10 – 4 10 –3 10 –2 10 –1 1 101 Input Voltage – V A1 – + Y Origin 1/2 TL441 + – Input A2 GND Y Output Slope Figure 12. Output Slope and Origin Adjustment 8 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 TL441AM LOGARITHMIC AMPLIFIER SLFS038 – JUNE 1976 – REVISED FEBRUARY 1989 APPLICATION INFORMATION TRANSFER CHARACTERISTICS OF TWO TYPICAL INPUT STAGES 0.4 Output Voltage – V 0.3 0.2 0.1 0 0.001 1 0.1 0.01 10 Input Voltage – V 2 kΩ, 1% B1 2 kΩ, 1% Z 20 kΩ 1/2 TL441 + – Output 2 kΩ, 1% Input B2 GND Z 2 kΩ, 1% Figure 13. Utilization of Separate Stages POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 9 TL441AM LOGARITHMIC AMPLIFIER SLFS038 – JUNE 1976 – REVISED FEBRUARY 1989 APPLICATION INFORMATION TRANSFER CHARACTERISTICS WITH BOTH SIDES PARALLELED 0.4 Output Voltage – V 0.3 0.2 0.1 0 0.001 0.01 0.1 1 10 Input Voltage – V 2 kΩ, 1% A1 Y A2 20 kΩ TL441 Input 2 kΩ, 1% Y – Z B1 + Output 2 kΩ, 1% B2 GND Z 2 kΩ, 1% Figure 14. Utilization of Paralleled Inputs 10 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 TL441AM LOGARITHMIC AMPLIFIER SLFS038 – JUNE 1976 – REVISED FEBRUARY 1989 APPLICATION INFORMATION TRANSFER CHARACTERISTICS 0.8 0.7 Output Voltage – V 0.6 0.5 0.4 0.3 0.2 0.1 0 10 – 4 10 –3 10 –2 10 –1 1 101 Input Voltage – V 2 kΩ A1 Y A2 Y VCC + = 4 V 1 kΩ 15 kΩ + – VCC – = – 4 V 5 kΩ 1 kΩ 20 kΩ 910 Ω B1 Z B2 Z + – VCC + = 4 V 2 kΩ + – 100 Ω Origin TL441 910 Ω Input 2 kΩ Slope 5 kΩ VCC – = – 4 V Output 5 kΩ 100 Ω 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 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 11 TL441AM LOGARITHMIC AMPLIFIER SLFS038 – JUNE 1976 – REVISED FEBRUARY 1989 APPLICATION INFORMATION R A1 Y TL441 A2 + Input A – R R R R + Y see Note A + – R B1 + B2 – Y 1/2 TL441 A2 Y + – Z Input B OUTPUT W (see Note B) A1 – Z R R R R NOTES: A. Connections shown are for multiplication. For division, Z and Z connections are reversed. 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. Multiplication: W = A • B ⇒ log W = log A + log B, or W = a(logaA + logaB) Division: W = A/B ⇒ log W = log A – log B, or W = a(logaA + logaB) Figure 16. Multiplication or Division R A1 Input A 1/2 TL441 + – A2 nR R R Y – R + – B1 + Y + – B2 1/2 TL441 Z Output W Z R nR R 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 loga A) Figure 17. Raising a Variable to a Fixed Power 12 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 TL441AM LOGARITHMIC AMPLIFIER SLFS038 – JUNE 1976 – REVISED FEBRUARY 1989 APPLICATION INFORMATION 2 kΩ Input A 2 kΩ Slope Origin – A1 + 20 kΩ + A2 1/2 TL441 Y Output W Y – 2 kΩ 2 kΩ NOTE: Adjust the slope to correspond to the base “a”. Exponential to any base: W = a. Figure 18. Raising a Fixed Number to a Variable Power 2.2 kΩ A1 Input 1 TL592 + – 0.2 µF 50 Ω 0.2 µF 0.2 µF 50 Ω Output 1 1 kΩ 1 kΩ Gain Adj. 2.2 kΩ Z 20 kΩ TL592 0.2 µF + – 0.2 µF Output 2 Z B2 Open + – TL441 B1 + – 0.2 µF 2.2 kΩ 50 Ω TL592 TL592 Y Gain Adj. = 400 Ω For 30 dB Input 2 20 kΩ A2 Open 50 Ω Y CA2 CA2’ CB2 CB2’ 10 10 kΩ kΩ 2.2 kΩ 1 kΩ 1 kΩ Gain Adj. 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 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 13 IMPORTANT NOTICE Texas Instruments and its subsidiaries (TI) reserve the right to make changes to their products or to discontinue any product or service without notice, and advise customers to obtain the latest version of relevant information to verify, before placing orders, that information being relied on is current and complete. All products are sold subject to the terms and conditions of sale supplied at the time of order acknowledgement, including those pertaining to warranty, patent infringement, and limitation of liability. TI warrants performance of its semiconductor products to the specifications applicable at the time of sale in accordance with TI’s standard warranty. Testing and other quality control techniques are utilized to the extent TI deems necessary to support this warranty. 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