GENERAL DESCRIPTION
The AD8313 is a complete multistage demodulating logarithmic amplifier that can accurately convert an RF signal at its differential input to an equivalent decibel-scaled value at its dc output. The AD8313 maintains a high degree of log conformance for signal frequencies from 0.1 GHz to 2.5 GHz and is useful over the range of 10 MHz to 3.5 GHz. The nominal input dynamic range is –65 dBm to 0 dBm (re: 50 Ω), and the sensitivity can be increased by 6 dB or more with a narrow-band input impedance matching network or a balun. Application is straightforward, requiring only a single supply of 2.7 V to 5.5 V and the addition of a suitable input and supply decoupling. Operating on a 3 V supply, its 13.7 mA consumption (for TA = 25°C) is only 41 mW. A power-down feature is provided; the input is taken high to initiate a low current (20 µA) sleep mode, with a threshold at half the supply voltage.

FEATURES
   Wide bandwidth: 0.1 GHz to 2.5 GHz min
   High dynamic range: 70 dB to ±3.0 dB
   High accuracy: ±1.0 dB over 65 dB range (@ 1.9 GHz)
   Fast response: 40 ns full-scale typical
   Controller mode with error output
   Scaling stable over supply and temperature
   Wide supply range: 2.7 V to 5.5 V
   Low power: 40 mW at 3 V
   Power-down feature: 60 mW at 3 V
   Complete and easy to use

APPLICATIONS
   RF transmitter power amplifier setpoint control and
      level monitoring
   Logarithmic amplifier for RSSI measurement cellular
      base stations, radio link, radar