PRODUCT DESCRIPTION
The AD606 is a complete, monolithic logarithmic amplifier using a 9-stage “successive-detection” technique. It provides both logarithmic and limited outputs. The logarithmic output is from a three-pole post-demodulation low-pass filter and provides a loadable output voltage of +0.1 V dc to +4 V dc. The logarithmic scaling is such that the output is +0.5 V for a sinusoidal input of –75 dBm and +3.5 V at an input of +5 dBm; over this range the logarithmic linearity is typically within ±0.4 dB. All scaling parameters are proportional to the supply voltage.
The AD606 can operate above and below these limits, with reduced linearity, to provide as much as 90 dB of conversion range. A second low-pass filter automatically nulls the input offset of the first stage down to the submicrovolt level. Adding external capacitors to both filters allows operation at input frequencies as low as a few hertz.

FEATURES
  Logarithmic Amplifier Performance
     –75 dBm to +5 dBm Dynamic Range
     ≤1.5 nV/√Hz Input Noise
     Usable to >50 MHz
     37.5 mV/dB Voltage Output
     On-Chip Low-Pass Output Filter
  Limiter Performance
     61 dB Output Flatness over 80 dB Range
     638 Phase Stability at 10.7 MHz over 80 dB Range
     Adjustable Output Amplitude
  Low Power
     +5 V Single Supply Operation
     65 mW Typical Power Consumption
     CMOS-Compatible Power-Down to 325 mW typ
     <5 ms Enable/Disable Time

APPLICATIONS
  Ultrasound and Sonar Processing
  Phase-Stable Limiting Amplifier to 100 MHz
  Received Signal Strength Indicator (RSSI)
  Wide Range Signal and Power Measurement