The AD8366 is a matched pair of fully differential, low noise and low distortion, digitally programmable variable gain amplifiers (VGAs). The gain of each amplifier can be programmed separately or simultaneously over a range of 4.5 dB to 20.25 dB in steps of 0.25 dB. The amplifier offers flat frequency performance from dc to 70 MHz, independent of gain code.

The AD8366 offers excellent spurious-free dynamic range, suitable for driving high resolution analog-to-digital converters (ADCs). The NF at maximum gain is 11.4 dB at 10 MHz and increases ~2 dB for every 4 dB decrease in gain. Over the entire gain range, the HD3/HD2 are better than −90 dBc for 2 V p-p at the output at 10 MHz into 200 Ω. The two-tone intermodulation distortion of −90 dBc into 200 Ω translates to an OIP3 of 45 dBm (38 dBVrms). The differential input impedance of 200 Ω provides a well-defined termination. The differential output has a low impedance of ~25 Ω.

The output common-mode voltage defaults to V_POS/2 but can be programmed via the VCMA and VCMB pins over a range of voltages. The input common-mode voltage also defaults to V_POS/2 but can be driven down to 1.5 V. A built-in, dc offset compensation loop can be used to eliminate dc offsets from prior stages in the signal chain. This loop can also be disabled if dc-coupled operation is desired.

The digital interface allows for parallel or serial mode gain programming. The AD8366 operates from a 4.75 V to 5.25 V supply and consumes typically 180 mA. When disabled, the part consumes roughly 3 mA. The AD8366 is fabricated using Analog Devices, Inc., advanced silicon-germanium bipolar process, and it is available in a 32-lead exposed paddle LFCSP package. Performance is specified over the −40°C to +85°C temperature range.

Applications