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

The model number is a specific version of a generic that can be purchased or sampled.

Status indicates the current lifecycle of the product. This can be one of 4 stages:

• Pre-Release: The model has not been released to general production, but samples may be available.
• Production: The model is currently being produced, and generally available for purchase and sampling.
• Last Time Buy: The model has been scheduled for obsolescence, but may still be purchased for a limited time.
• Obsolete: The specific part is obsolete and no longer available. Other models listed in the table may still be available (if they have a status that is not obsolete).

The package for this IC (i.e. DIP, SOIC, BGA). An Evaluation Board is a board engineered to show the performance of the model, the part is included on the board.

For detailed drawings and chemical composition please consult our  Package Site

Pin Count is the number of pins, balls, or pads on the device. Pin-out diagrams & pin function descriptions may be found in the datasheet.

This is the acceptable operating range of the device. The various ranges specified are as follows:

• Commercial: 0 to +70 degrees Celsius
• Military : -55 to +125 degrees Celsius
• Industrial: Temperature ranges may vary by model. Please consult the datasheet for more information.
• Automotive: -40 to +125 degrees Celsius

The USA list pricing shown is for BUDGETARY USE ONLY, shown in United States dollars (FOB USA per unit for the stated volume), and is subject to change. International prices may differ due to local duties, taxes, fees and exchange rates. For volume-specific price or delivery quotes, please contact your local Analog Devices, Inc. sales office or authorized distributor. Pricing displayed for Evaluation Boards and Kits is based on 1-piece pricing.

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