250 MHz Demodulating a Logarithmic Amplifier AD641 FEATURES PIN CONFIGURATIONS Logarithmic Amplifier Performance 20-Lead Plastic DIP (N) Usable to 250 MHz 20-Lead Cerdip (Q) 44 dB Dynamic Range 62.0 dB Log Conformance 1 20 INPUT +INPUT 37.5 mV/dB Voltage Output 2 19 ATN LO ATN OUT Stable Slope and Intercepts 3 18 ATN COM CKT COM 2.0 nV/ Hz Input Noise Voltage ATN COM 4 17 RG1 50 mV Input Offset Voltage ATN IN 5 16 RG0 Low Power AD641 TOP VIEW BL1 6 15 RG2 65 V Supply Operation (Not to Scale) 9 mA (+V ), 35 mA (V ) Quiescent Current V 7 14 LOG OUT S S S Onboard Resistors ITC 8 13 LOG COM Onboard 103 Attenuator BL2 9 12 +V S Dual Polarity Current Outputs OUTPUT 10 11 +OUTPUT Direct Coupled Differential Signal Path APPLICATIONS 20-Lead PLCC (P) IF/RF Signal Processing Received Signal Strength Indicator (RSSI) High Speed Signal Compression High Speed Spectrum Analyzer ECM/Radar 3 2 1 20 19 PIN 1 ATN COM 4 18 CKT COM IDENTIFIER PRODUCT DESCRIPTION ATN IN 5 17 RG1 AD641 The AD641 is a 250 MHz, demodulating logarithmic amplifier 6 16 BL1 RG0 TOP VIEW with an accuracy of 2.0 dB and 44 dB dynamic range. The (Not to Scale) V 7 15 RG2 S AD641 uses a successive detection architecture to provide an 8 14 ITC LOG OUT output current that is logarithmically proportional to its input 9 10 11 12 13 voltage. The output current can be converted to a voltage using one of several on-chip resistors to select the slope. A single AD641 provides up to 44 dB of dynamic range at speeds up to 250 MHz, and two cascaded AD641s together can provide 58 dB of dynamic range at speeds up to 250 MHz. The AD641 is fully stable and well characterized over either the industrial or The 250 MHz bandwidth and temperature stability make this military temperature ranges. product ideal for high speed signal power measurement in RF/ IF systems. ECM/Radar and Communication applications are The AD641 is not a logarithmic building block, but rather a routinely in the 100 MHz180 MHz range for power measure- complete logarithmic solution for compressing and measuring ment. The bandwidth and accuracy, as well as dynamic range, wide dynamic range signals. The AD641 is comprised of five make this part ideal for high speed, wide dynamic range signals. stages and each stage has a full wave rectifier, whose current depends on the absolute value of its input voltage. The output The AD641 is offered in industrial (40 C to +85 C) and mili- of these stages are summed together to provide the demodulated tary (55 C to +125 C) package temperature ranges. Industrial output current scaled at 1 mA per decade (50 m A/dB). versions are available in plastic DIP and PLCC MIL versions are packaged in cerdip. Without utilizing the 10 input attenuator, log conformance of 2.0 dB is maintained over the input range 44 dBm to 0 dBm. The attenuator offers the most flexibility without significantly impacting performance. 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 which may result from its use. No license is granted by implication or Tel: 781/329-4700 World Wide Web Site: AD641SPECIFICATIONS ELECTRICAL CHARACTERISTICS (V = 65 V T = +258C, unless otherwise noted) S A AD641A AD641S Parameter Conditions 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 LOG AMPLIFIER PERFORMANCE 3 dB Bandwidth 250 250 MHz Voltage Compliance Range 0.3 +V 1 0.3 +V 1 V S S Slope Current, I 0.98 1.00 1.02 0.98 1.00 1.02 mA Y Accuracy vs. Temperature 0.002 0.002 %/ C Over Temperature T to T 0.96 1.02 mA MIN MAX Intercept dBm 250 MHz 41.06 40.51 39.96 41.06 40.51 39.96 dBm Over Temperature T to T , 250 MHz 41.34 39.47 dBm MIN MAX 2 Zero Signal Output Current 0.2 0.2 mA ITC Disabled Pin 8 to COM 0.27 0.27 mA Maximum Output Current 2.3 2.3 mA DYNAMIC RANGE Single Configuration 44 44 dB Over Temperature T to T 40 38 dB MIN MAX Dual Configuration 58 58 dB Over Temperature T to T 52 52 dB MIN MAX LOG CONFORMANCE f = 250 MHz Single Configuration 44 dBm to 0 dBm 0.5 2.0 0.5 2.0 dB Over Temperature 42 dBm to 4 dBm T to T 1.0 2.5 dB MIN MAX 42 dBm to 2 dBm, T to T 1.0 2.5 MIN MAX Dual Configuration S: 60 dBm to 2 dBm 0.5 2.0 0.5 2.0 dB Over Temperature A: 56 dBm to 4 dBm, T to T 1.0 2.5 1.0 2.5 dB MIN MAX LIMITER CHARACTERISTICS Flatness 44 dBm to 0 dBm 10.7 MHz 1.6 1.6 dB Phase Variation 44 dBm to 0 dBm 10.7 MHz 2.0 2.0 Degrees INPUT CHARACTERISTICS Input Resistance Differential 500 500 kW Input Offset Voltage Differential 50 200 50 200 m V vs. Temperature 0.8 0.8 m V/ C Over Temperature T to T 300 m V MIN MAX vs. Supply 22 m V/V Input Bias Current 7 25 7 25 m A Input Bias Offset 11 m A Common Mode Input Range 2 +0.3 2 +0.3 V SIGNAL INPUT (Pins 1, 20) Input Capacitance Either Pin to COM 2 2 pF Noise Spectral Density 1 kHz to 10 MHz 2 2 nV/ Hz Tangential Sensitivity BW = 100 MHz 72 72 dBm INPUT ATTENUATOR (Pins 2, 3, 4, 5 & 19) 3 Attenuation Pins 5 to Pin 19 20 20 dB Input Resistance Pins 5 to 3/4 300 300 W APPLICATION RESISTORS (Pins 15, 16, 17) 0.995 1.000 1.005 0.995 1.000 1.005 kW OUTPUT CHARACTERISTICS (Pins 10, 11) 4 Peak Differential Output 180 180 mV Output Resistance Either Pin to COM 75 75 W Quiescent Output Voltage Either Pin to COM 90 90 mV POWER SUPPLY Voltage Supply Range 4.5 7.5 4.5 7.5 V Quiescent Current +V (Pin 12) T to T 915 9 15 mA S MIN MAX V (Pin 7) T to T 35 60 35 60 mA S MIN MAX NOTES 1 Logarithms to base 10 are used throughout. The response is independent of the sign of V . IN 2 The zero-signal current is a function of temperature unless internal temperature compensation (ITC) pin is grounded. 3 Attenuation ratio trimmed to calibrate intercept to 10 mV when in use. It has a temperature coefficient of +0.3%/ C. 4 The fully limited signal output will appear to be a square wave its amplitude is proportional to absolute temperature. Specifications subject to change without notice. 2 REV. D