Analog Devices, Inc. extends its leadership position in RF/IF Measurement and Control ICs by announcing a 500-MHz, 100-dB logarithmic amplifier, the AD8309. Until now, it required a lot of work to coax the kind of dynamic range engineers needed from their high-frequency transceiver designs. The AD8309 provides both logarithmic and limiter outputs for accurate phase detection in PSK (phase-shift keying) and FSK (frequency-shift keying) applications including CDMA (Code Division Multiple Access) and GSM (Global System for Mobile communications).

Designed with attention to ease-of-implementation, temperature stability, minimizing of external components, low power and low cost, the AD8309 detects the RF envelope of the signal, so engineers do not have to demodulate it. The limiter outputs provide a hard-limited signal as a differential current from open collector outputs. The output buffer provides an adjustable and temperature-stable output.

The 500-MHz bandwidth, high accuracy and temperature stability make this product well-suited for high-speed signal strength measurement in RF/IF applications such as cellular basestations and radar. The bandwidth, accuracy, dynamic range and low noise also make this log amp well-suited for applications which require wide dynamic range capability for compression (log conversion) prior to digitization. For more information on logarithmic amplifiers, including tutorials, application notes and samples, click here.

When I reviewed the AD8313 (2.5-GHz, 65-dB dynamic range log amp) in August 1998 I said that there was a market for a device at about a quarter of the price and with less dynamic range for IFs. Well, this isn't it. This is a cool product, with a fantastic dynamic range and is overkill for the applications I was contemplating which would be consumer sales levels. It does, however, have its own market in the phase detection part of high-end systems and will be extremely profitable for the company in those uses. I doubt whether the price level will allow it entry into some of the less demanding applications such as pure signal strength measurements for which the higher-frequency AD8313 is probably still most suited. But these products are unique and I hope that Analog keeps producing more specialized versions.

The part is fully specified at both +3 V and +5 V and is suitable for use in harsh conditions with an operating temperature range from -40 to +85ýC

The AD8309 is in a 16-lead TSSOP and is priced at $7.75 in 1000-piece lots.