The AD640JPZ is a complete monolithic logarithmic amplifier. A singleAD640JPZ provides up to 50 dB of dynamic range for frequenciesfrom dc to 120 MHz. Two AD640s in cascade can provide up to95 dB of dynamic range at reduced bandwidth. The AD640JPZ uses asuccessive detection scheme to provide an output current proportionalto the logarithm of the input voltage. It is laser calibrated toclose tolerances and maintains high accuracy over the full militarytemperature range using supply voltages from ±4.5 V to ±7.5 V.
The AD640JPZ comprises five cascaded dc-coupled amplifier/limiterstages, each having a small signal voltage gain of 10 dB and a –3 dBbandwidth of 350 MHz. Each stage has an associated full-wavedetector, whose output current depends on the absolute value of itsinput voltage. The five outputs are summed to provide the videooutput (when low-pass filtered) scaled at 1 mA per decade (50 µAper dB). On chip resistors can be used to convert this output currentto a voltage with several convenient slope options. A balancedsignal output at +50 dB (referred to input) is provided to operateAD640s in cascade.
The logarithmic response is absolutely calibrated to within ±1 dBfor dc or square wave inputs from ±0.75 mV to ±200 mV, withan intercept (logarithmic offset) at 1 mV dc. An integral X10attenuator 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 MILSTD-883B,for the military range of –55°C to +125°C. Both areavailable in 20-lead side-brazed ceramic DIPs or leadless chipcarriers (LCC). The AD640J is specified for the commercialtemperature range of 0°C to +70°C, and is available in both20-lead plastic DIP (N) and PLCC (P) packages.This device is now available to Standard Military Drawing(DESC) number 5962-9095501MRA and 5962-9095501M2A.
Product Highlights
Feature
- 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 Options (1 V/Decade, 100 mV/dB, etc.)
- Low power operation (typically 220 mW at 65 V)
- Low cost plastic packages also available
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
(Picture: Pinout)
