The AD8366 is a matched pair of fully differential low-noise and low-distortion digitally programmable variable gain amplifiers. The gain of each amplifier can be programmed separately or simultaneously over a range of 5 dB to 21 dB in steps of 0.25 dB. The amplifier offers flat frequency performance and group delay from DC out to 150 MHz, independent of gain code.
The AD8366 offers excellent spurious-free dynamic range, suitable for driving 12-bit ADCs. The NF at max gain is 10.5 dB at 10 MHz and increases 2dB for every 4dB decrease in gain. Over the entire gain range, the HD3 and HD2 are >88dBc for 2 V p-p at the output at 10 MHz into 500 Ω. The 2-tone intermodulation distortion of -90dBc into 200 Ω translates to an OIP3 of 43 dBm. The differential input impedance is 200 Ω to provide a well-defined termination. The differential output is voltage-mode with a low impedance of 30 Ω.
The output common-mode defaults to Vps/2 but can be programmed via pins VCMA and VCMB over a range of voltages. The built-in DC-offset compensation loop can be disabled if DC-coupled operation is desired. The high-pass corner is defined by external capacitors on pins OFSA and OFSB. The input common mode also defaults to Vps/2 but can be driven from 1.2V to 3.4V.
The digital interface allows for parallel or serial gain programming. The AD8366 operates off a 4.5V to 5.5V supply and consumes a supply current of 175mA. When disabled, it consumes ~ 4mA. The AD8366 is fabricated using Analog Devices’ advanced Silicon-Germanium bipolar process and is available in a 32-lead exposed paddle LFCSP package. Performance is specified over a -40oC to +85oC temperature range.