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

APPLICATIONS

Ultrasound and Sonar Processing

Phase-Stable Limiting Amplifier to 100 MHz

Received Signal Strength Indicator (RSSI)

Wide Range Signal and Power Measurement