The AD641APZ is a 250 MHz, demodulating logarithmic amplifierwith an accuracy of ±2.0 dB and 44 dB dynamic range. TheAD641APZ uses a successive detection architecture to provide anoutput current that is logarithmically proportional to its inputvoltage. The output current can be converted to a voltage usingone of several on-chip resistors to select the slope. A singleAD641APZ provides up to 44 dB of dynamic range at speeds up to250 MHz, and two cascaded AD641s together can provide58 dB of dynamic range at speeds up to 250 MHz. The AD641is fully stable and well characterized over either the industrial ormilitary temperature ranges.
The AD641APZ is not a logarithmic building block, but rather acomplete logarithmic solution for compressing and measuringwide dynamic range signals. The AD641APZ is comprised of fivestages and each stage has a full wave rectifier, whose currentdepends on the absolute value of its input voltage. The outputof these stages are summed together to provide the demodulatedoutput current scaled at 1 mA per decade (50 µA/dB).
Without utilizing the 10× input attenuator, log conformance of2.0 dB is maintained over the input range –44 dBm to 0 dBm.The attenuator offers the most flexibility without significantlyimpacting performance.
The 250 MHz bandwidth and temperature stability make thisproduct ideal for high speed signal power measurement in RF/IF systems. ECM/Radar and Communication applications areroutinely in the 100 MHz–180 MHz range for power measurement.The bandwidth and accuracy, as well as dynamic range,make this part ideal for high speed, wide dynamic range signals.The AD641APZ is offered in industrial (–40°C to +85°C) and military(–55°C to +125°C) package temperature ranges. Industrialversions are available in plastic DIP and PLCC; MIL versionsare packaged in cerdip.
Feature
- Logarithmic amplifier performance
- Usable to 250 MHz
- 44 dB dynamic range
- ±2.0 dB log conformance
- 37.5 mV/dB voltage output
- Stable slope and intercepts
- 2.0 nV/√Hz input noise voltage
- 50 mV input offset voltage
- Low power
- ±5 V supply operation
- 9 mA (+VS), 35 mA (–VS) quiescent current
- Onboard resistors
- Onboard 10× attenuator
- Dual polarity current outputs
- Direct coupled differential signal path
Applications
- IF/RF signal processing
- Received Signal Strength Indicator (RSSI)
- High speed signal compression
- High speed spectrum analyzer
- ECM/radar
(Picture: Pinout)
