AD641–Typical DC Performance Characteristics1.0151.201.0061.0101.151.0041.0051.101.00211.051.0000.9951.000.9980.990INTERCEPT – mV 0.95SLOPE CURRENT – mASLOPE CURRENT – mV0.9960.9850.900.9800.850.994–60 –40 –2002040 60 80 100 120 140–60 –40 –2002040 60 80 100 120 1404.55.05.56.06.57.07.5TEMPERATURE – 8 CTEMPERATURE – 8 CPOWER SUPPLY VOLTAGES – 6 Volts Figure 1. Slope Current, I Figure 3. Slope Current, I Y, vs. Figure 2. Intercept Voltage, VX, vs. Y, vs. Supply Temperature Temperature Voltages 1.01514+0.413+0.31.010INPUT OFFSET VOLTAGE12+0.2DEVIATION WILL BE WITHIN1.005SHADED AREA.11+0.11.0001000.995INTERCEPT – mV 9–0.1INTERCEPT VOLTAGE – mV 0.9908–0.20.9857–0.34.55.05.56.06.57.07.5–60 –40 –20 0204060 80 100 120 140–60 –40 –200204060 80 100 120 140DEVIATION OF INPUT OFFSET VOLTAGE – mVPOWER SUPPLY VOLTAGES – 6 VoltsTEMPERATURE – 8 CTEMPERATURE – 8 C Figure 4. Intercept Voltage, V Figure 6. Input Offset Voltage Devia- X, vs. Figure 5. Intercept Voltage (Using Supply Voltages Attenuator) vs. Temperature tion vs. Temperature 22.52.52.412.202.02.02.01.8 1.6 1.41.51.51.2 1.0 0.81.01.00.6 0.4ERROR – dB0.2OUTPUT CURRENT – mAABSOLUTE ERROR – dB 0.5ABSOLUTE ERROR – dB 0.50–0.2 –0.4000.11.010.0100.01000.0–60 –40 –20020 40 6080 100 120 140–60 –40 –2002040 6080 100 120 140INPUT VOLTAGE – mVTEMPERATURE – 8 CTEMPERATURE – 8 C(EITHER SIGN) Figure 8. Absolute Error vs. Tempera- Figure 7. DC Logarithmic Transfer Figure 9. Absolute Error vs. Tempera- Function and Error Curve for Single ture, VIN = ±1 mV to ±100 mV ture, Using Attenuator. VIN = ±10 mV AD641 to ±1 V, Pin 8 Grounded to Disable ITC Bias –4– REV. D Document Outline FEATURES PRODUCT DESCRIPTION PIN CONFIGURATIONS AD641--SPECIFICATIONS ELECTRICAL CHARACTERISTICS THERMAL CHARACTERISTICS ABSOLUTE MAXIMUM RATINGS ESD CAUTION REVISION HISTORY AD641--TYPICAL DC PERFORMANCE CHARACTERISTICS TYPICAL AC PERFORMANCE CHARACTERISTICS CIRCUIT DESCRIPTION CIRCUIT OPERATION FUNDAMENTALS OF LOGARITHMIC CONVERSION INTERCEPT STABILIZATION CONVERSION RANGE EFFECT OF WAVEFORM ON INTERCEPT LOGARITHMIC CONFORMANCE AND WAVEFORM SIGNAL MAGNITUDE INTERCEPT AND LOGARITHMIC OFFSET OPERATION OF A SINGLE AD641 ACTIVE CURENT-TO-VOLTAGE CONVERSION EFFECT OF FREQUENCY ON CALIBRATION SOURCE RESISTANCE AND INPUT OFFSET USING HIGHER SUPPLY VOLTAGES USING THE ATTENUATOR OPERATION OF CASCADED AD641s ELIMINATING THE EFFECT OF FIRST STAGE OFFSET PRACTICAL APPLICATIONS RSSI APPLICATIONS 250 MHz RSSI CONVERTER WITH 58 dB DYNAMIC RANGE OUTLINE DIMENSIONS ORDERING GUIDE