DC-Coupled Demodulating a 120 MHz Logarithmic Amplifier AD640 FEATURES signal output at +50 dB (referred to input) is provided to operate Complete, Fully Calibrated Monolithic System AD640s in cascade. Five Stages, Each Having 10 dB Gain, 350 MHz BW The logarithmic response is absolutely calibrated to within 1 dB Direct Coupled Fully Differential Signal Path for dc or square wave inputs from 0.75 mV to 200 mV, with Logarithmic Slope, Intercept and AC Response are an intercept (logarithmic offset) at 1 mV dc. An integral X10 Stable Over Full Military Temperature Range attenuator provides an alternative input range of 7.5 mV to Dual Polarity Current Outputs Scaled 1 mA/Decade 2 V dc. Scaling is also guaranteed for sinusoidal inputs. Voltage Slope Options (1 V/Decade, 100 mV/dB, etc.) The AD640B is specified for the industrial temperature range of Low Power Operation (Typically 220 mW at 65 V) 40 C to +85 C and the AD640T, available processed to MIL- Low Cost Plastic Packages Also Available STD-883B, for the military range of 55 C to +125 C. Both are APPLICATIONS available in 20-lead side-brazed ceramic DIPs or leadless chip Radar, Sonar, Ultrasonic and Audio Systems carriers (LCC). The AD640J is specified for the commercial Precision Instrumentation from DC to 120 MHz temperature range of 0 C to +70 C, and is available in both Power Measurement with Absolute Calibration 20-lead plastic DIP (N) and PLCC (P) packages. Wide Range High Accuracy Signal Compression This device is now available to Standard Military Drawing Alternative to Discrete and Hybrid IF Strips (DESC) number 5962-9095501MRA and 5962-9095501M2A. Replaces Several Discrete Log Amp ICs PRODUCT HIGHLIGHTS PRODUCT DESCRIPTION 1. Absolute calibration of a wideband logarithmic amplifier is The AD640 is a complete monolithic logarithmic amplifier. A single unique. The AD640 is a high accuracy measurement device, AD640 provides up to 50 dB of dynamic range for frequencies not simply a logarithmic building block. from dc to 120 MHz. Two AD640s in cascade can provide up to 2. Advanced design results in unprecedented stability over the 95 dB of dynamic range at reduced bandwidth. The AD640 uses a full military temperature range. successive detection scheme to provide an output current propor- 3. The fully differential signal path greatly reduces the risk of tional to the logarithm of the input voltage. It is laser calibrated to instability due to inadequate power supply decoupling and close tolerances and maintains high accuracy over the full military shared ground connections, a serious problem with com- temperature range using supply voltages from 4.5 V to 7.5 V. monly used unbalanced designs. The AD640 comprises five cascaded dc-coupled amplifier/limiter 4. Differential interfaces also ensure that the appropriate ground stages, each having a small signal voltage gain of 10 dB and a 3 dB connection can be chosen for each signal port. They further bandwidth of 350 MHz. Each stage has an associated full-wave increase versatility and simplify applications. The signal input detector, whose output current depends on the absolute value of its impedance is ~500 kW in shunt with ~2 pF. input voltage. The five outputs are summed to provide the video 5. The dc-coupled signal path eliminates the need for numerous output (when low-pass filtered) scaled at 1 mA per decade (50 m A interstage coupling capacitors and simplifies logarithmic per dB). On chip resistors can be used to convert this output cur- conversion of subsonic signals. rent to a voltage with several convenient slope options. A balanced (continued on page 4) FUNCTIONAL BLOCK DIAGRAM RG1 RG0 RG2 LOG OUT LOG COM 1kV 1kV 12 +V INTERCEPT POSITIONING BIAS 17 16 15 14 13 S COM 18 FULL-WAVE FULL-WAVE FULL-WAVE FULL-WAVE ATN OUT 19 FULL-WAVE DETECTOR DETECTOR DETECTOR DETECTOR DETECTOR 20 SIG +IN 11 SIG +OUT 10dB 10dB 10dB 10dB 10dB SIG IN 1 10 SIG OUT AMPLIFIER/LIMITER AMPLIFIER/LIMITER AMPLIFIER/LIMITER AMPLIFIER/LIMITER AMPLIFIER/LIMITER ATN LO 2 27V ATN COM 3 9 BL2 30V 270V 5 6 GAIN BIAS REGULATOR 7 SLOPE BIAS REGULATOR ATN COM 4 8 ITC ATN IN BL1 V S REV. D Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. use, nor for any infringements of patents or other rights of third parties Tel: 781/329-4700 World Wide Web Site: AD640SPECIFICATIONS (V = 65 V, T = +258C, unless otherwise noted) DC SPECIFICATIONS S A Model AD640J AD640B AD640T Parameter Conditions Min Typ Max Min Typ Max Min Typ Max Units 1 TRANSFER FUNCTION I = I LOG V /V for V = 0.75 mV to 200 mV dc OUT Y IN X IN SIGNAL INPUTS (Pins 1, 20) Input Resistance Differential 500 500 500 kW Input Offset Voltage Differential 50 500 50 200 50 200 m V vs. Temperature 0.8 0.8 0.8 m V/ C to T 300 m V Over Temperature TMIN MAX vs. Supply 2 2 2 m V/V Input Bias Current 7 25 7 25 7 25 m A Input Bias Offset 1 1 1 m A Common-Mode Range 2 +0.3 2 +0.3 2 +0.3 V INPUT ATTENUATOR (Pins 2, 3, 4, 5 and 19) 2 Pin 5 to Pin 19 20 20 20 dB Attenuation Input Resistance Pins 5 to 3/4 300 300 300 W SIGNAL OUTPUT (Pins 10, 11) 3 Small Signal Gain 50 50 50 dB 4 180 180 180 mV Peak Differential Output Output Resistance Either Pin to COM 75 75 75 W Quiescent Output Voltage Either Pin to COM 90 90 90 mV 5 LOGARITHMIC OUTPUT (Pin 14) 1 0.3 +V 1 0.3 V 1 V Voltage Compliance Range 0.3 +VS S S Slope Current, I 0.95 1.00 1.05 0.98 1.00 1.02 0.98 1.00 1.02 mA Y Accuracy vs. Temperature 0.002 0.002 0.002 %/ C T to T 0.9 6 1.02 mA MIN MAX = 4.5 V to 7.5 V 0.08 1.0 0.08 0.4 0.08 0.4 %/V Accuracy vs. Supply +VS 6 Intercept Voltage , V 0.85 0.99 1.15 0.93 0.99 1.05 0.9 3 0.99 1.05 mV X vs. Temperature 0.5 0.5 0.5 m V/ C Over Temperature T to T 0.90 1.10 mV MIN MAX = 4.5 V to 7.5 V 2 2 2 m V/V vs. Supply VS Logarithmic Offset ) 61.5 60.0 58.7 60.5 60.0 59.5 60.5 60.0 59.5 dBV (Alt. Definition of VX vs. Temperature 0.004 0.004 0.004 dB/ C to T 60.9 59.1 dB Over Temperature TMIN MAX vs. Supply V = 4.5 V to 7.5 V 0.017 0.017 0.017 dB/V S Intercept Voltage Using Attenuator 8.25 10.0 11.75 9.0 10.0 11.0 9.0 10.0 11.0 mV 7 Zero Signal Output Current 0.2 0.2 0.2 mA ITC Disabled Pin 8 to COM 0.27 0.27 0.27 mA Maximum Output Current 2.3 2.3 2.3 mA APPLICATIONS RESISTORS (Pins 15, 16, 17) 1.000 0.995 1.000 1.005 0.995 1.000 1.005 kW DC LINEARITY V 1 mV to 100 mV 0.35 1.2 0.35 0.6 0.35 0.6 dB IN TOTAL ABSOLUTE DC ACCURACY 8 V = 1 mV to 100 mV 0.55 2 0.55 1. 2 0.55 1. 2 dB IN to T 3 2. 0 2. 0 dB Over Temperature TMIN MAX Over Supply Range V = 4.5 V to 7.5 V 2 1. 5 1. 5 dB S = 0.75 mV to 200 mV 1.0 3 1.0 2.0 1.0 2.0 dB VIN Using Attenuator = 10 mV to 1 V 0.4 2.5 0.4 1.5 0.4 1.5 dB VIN Over Temperature T to T 0.6 3 0.6 2. 2 0.6 2. 2 dB MIN MAX V = 7.5 mV to 2 V 1.2 3.5 1.2 2.5 1.2 2.5 dB IN POWER REQUIREMENTS 64.5 67.5 64.5 67.5 64.5 67.5 V Voltage Supply Range 9 Quiescent Current +V (Pin 12) T to T 915 9 15 9 15 mA S MIN MAX V (Pin 7) T to T 35 60 35 60 35 60 mA S MIN MAX REV. 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