AD640:  120 MHz, 50 dB Demodulating Logarithmic Amplifier

The AD640 is a complete monolithic logarithmic amplifier. A single AD640 provides up to 50 dB of dynamic range for frequencies from dc to 120 MHz. Two AD640s in cascade can provide up to 95 dB of ...More

AD640:  120 MHz, 50 dB Demodulating Logarithmic Amplifier

Product Description

The AD640 is a complete monolithic logarithmic amplifier. A single AD640 provides up to 50 dB of dynamic range for frequencies from dc to 120 MHz. Two AD640s in cascade can provide up to 95 dB of dynamic range at reduced bandwidth. The AD640 uses a successive detection scheme to provide an output current proportional to the logarithm of the input voltage. It is laser calibrated to close tolerances and maintains high accuracy over the full military temperature range using supply voltages from ±4.5 V to ±7.5 V.

The AD640 comprises five cascaded dc coupled amplifier/limiter stages, each having a small signal voltage gain of 10 dB and a -3 dB bandwidth of 350 MHz. Each stage has an associated full-wave detector, whose output current depends on the absolute value of its input voltage. The five outputs are summed to provide the video output (when low-pass filtered) scaled at 1 mA per decade (50 µA per dB). On chip resistors can be used to convert this output current to a voltage with several convenient slope options. A balanced signal output at +50 dB (referred to input) is provided to operate AD640s in cascade.

The logarithmic response is absolutely calibrated to within ±l dB for dc or square wave inputs from ±0.75 mV to ±200 mV,with an intercept (logarithmic offset) at 1 mV dc. An integral X10 attenuator provides an alternative input range of ±7.5 mV to ±2 V dc. Scaling is also guaranteed for sinusoidal inputs.

The AD640B is specified for the industrial temperature range of -40°C to +85°C and the AD640T, available processed to MIL-STD- 883B, for the military range of -55°C to +125°C. Both are available in 20-pin side brazed ceramic DIPs or leadless chip carriers (LCC). The AD640J is specified for the commercial temperature range of 0°C to +70°C, and is available in both 20-pin plastic DIP (N) and PLCC (P) packages.

This device is now available to Standard Military Drawing (DESC) number 5962-9095501MRA and 5962-9095501M2A.

An evaluation board is available for this product and may be ordered using the following product number: AD640-EB.

Applications

  • Radar, Sonar, Ultrasonic and Audio Systems
  • Precision Instrumentation from DC to 120 MHz
  • Power Measurement with Absolute Calibration
  • Wide Range High Accuracy Signal Compression
  • Alternative to Discrete and Hybrid IF Strips
  • Replaces Several Discrete Log Amp ICs

    • Features

    • Complete, Fully Calibrated Monolithic System
    • Five Stages, Each Having 10 dB Gain,
      350 MHz BW
    • Direct Coupled Fully Differential Signal Path
    • Logarithmic Slope, Intercept and AC Response are Stable Over Full Military Temperature Range
    • Dual Polarity Current Outputs Scaled
      1 mA/Decade
    • Voltage Slope Operation (1 V/Decade,
      100 mV/dB, etc.)
    • Low Power Operation (Typically 220 mW at
      ±5 V)
    • Low Cost Plastic Packages Also Available

    Diagrams

    AD640 Diagram
    Functional Block Diagram for AD640

    Specifications

    Dynamic Range (dB) 50dB
    Temp Stability (dB) ±1dB
    Phase Accuracy (deg) n/a
    Response Time (ns typ) 10ns
    Voltage Supply (V) +/- 4.5 to +/- 7.5
    Supply Current (max) 44mA
    Limiter Output Yes
    AC Linearity (± dB) 3dB
    Power Consumption (mW) 200mW
    Package 20-Lead DIP,20-Lead LCC,20-Lead PLCC

    ADL5513 - 1 MHz to 4 GHz, 80 dB Logarithmic Detector/Controller

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    Part# Product Description RF Frequency (MHz) Dynamic Range (dB) Temp Stability (dB) Response Time (ns typ) Voltage Supply (V) Supply Current (max) Package Price* (1000-4999)
    AD606 Limiter Output - 80 - 400 4.5 to 5.5 13 16-Lead DIP, 16-Lead SOIC $22.00
    AD640 Military Specified Part Available - 50 ±1 10 +/- 4.5 to +/- 7.5 44 20-Lead DIP, 20-Lead LCC, 20-Lead PLCC $36.48
    AD641 Military Specified Part Available - 44 ±1 10 +/- 4.5 to +/- 7.5 44 20-Lead DIP, 20-Lead LCC, 20-Lead PLCC $32.82
    AD8302 Dual-Channel Gain and Phase Outputs 2,700 60 ±1 60 2.7 to 5.5 19 14-Lead TSSOP $12.14
    AD8306 Military Specified Part Available 5 to 400 100 ±1 73 2.7 to 5.5 16 16-Lead SOP $14.67
    AD8307 High Dynamic Range dc to 500 92 ±1 400 2.7 to 5.5 8 8-Lead SOIC/DIP $6.07
    AD8309 Limiter Output 5 to 500 100 ±1 67 2.7 to 5.5 16 16-Lead TSSOP $7.84
    AD8310 High Dynamic Range dc to 440 100 ±1 15 2.7 to 5.5 8 8-Lead SOIC $4.00
    AD8311 Low Power for Battery Operation 100 to 2500 50 ±0.5 150 2.7 to 5.5 8.5 WLCSP $1.27
    AD8312 Low Power for Battery Operation 50 to 3500 45 ±0.5 70 2.7 to 5.5 4.2 WLCSP $1.27
    AD8313 Industry Standard 100 to 2500 70 ±1.25 40 2.7 to 5.5 14 8-Lead uSOIC $7.99
    AD8314 Industry Standard 100 to 2700 45 ±1 70 2.7 to 5.5 4.5 8-Lead uSOIC/CSP $1.10
    AD8315 Low Power for Battery Operation 100 to 2500 50 ±1 150 2.7 to 5.5 8.5 8-Lead uSOIC $4.00
    AD8317 Available in Die 1 to 10000 55 ±0.5 6 3 to 5.5 20 8-Lead CSP $3.98
    AD8318 Integrated Temp Sensor 1 to 8000 70 ±0.5 10 4.5 to 5.5 68 16-Lead CSP $5.05
    AD8319 Pin-compatible with AD8317 1 to 10000