AD8307ARZ Low Cost DC-500 MHz, 92 dB Logarithmic Amplifier 100 watt led diodes

AD8307ARZ Low Cost DC-500 MHz, 92 dB Logarithmic Amplifier 100 watt led diodes

FEATURES Complete multistage logarithmic amplifier 92 dB dynamic range: –75 dBm to +17 dBm to –90 dBm using matching network Single supply of 2.7 V minimum at 7.5 mA typ DC to 500 MHz operation, ±1 dB linearity Slope of 25 mV/dB, intercept of −84 dBm Highly stable scaling over temperature Fully differential dc-coupled signal path 100 ns power-up time, 150 μA sleep current

APPLICATIONS Conversion of signal level to decibel form Transmitter antenna power measurement Receiver signal strength indication (RSSI) Low cost radar and sonar signal processing Network and spectrum analyzers (to 120 dB) Signal level determination down to 20 Hz True decibel ac mode for multimeters

GENERAL DESCRIPTION The AD8307 is the first logarithmic amplifier made available in an 8-lead (SOIC-8) package. It is a complete 500 MHz monolithic demodulating logarithmic amplifier based on the progressive compression (successive detection) technique, providing a dynamic range of 92 dB to ±3 dB law-conformance and 88 dB to a tight ±1 dB error bound at all frequencies up to 100 MHz. It is extremely stable and easy to use, requiring no significant external components. A single-supply voltage of 2.7 V to 5.5 V at 7.5 mA is needed, corresponding to an unprecedented power consumption of only 22.5 mW at 3 V. A fast acting CMOScompatible control pin can disable the AD8307 to a standby current of less than 150 μA.

Each of the cascaded amplifier/limiter cells has a small signal gain of 14.3 dB, with a −3 dB bandwidth of 900 MHz. The input is fully differential and at a moderately high impedance (1.1 kΩ in parallel with about 1.4 pF). The AD8307 provides a basic dynamic range extending from approximately −75 dBm (where dBm refers to a 50 Ω source, that is, a sine amplitude of about ±56 μV) up to +17 dBm (a sine amplitude of ±2.2 V). A simple input matching network can lower this range to –88 dBm to +3 dBm. The logarithmic linearity is typically within ±0.3 dB up to 100 MHz over the central portion of this range, and degrades

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