AD8327

The AD8327 is a low-cost, digitally controlled, variable gain amplifier optimized for coaxial line driving applications such as cable modems that are designed to the MCNS-DOCSIS upstream standard. An 8-bit serial word determines the desired output gain over a 48.16 dB range resulting in gain changes of 6.02 dB/major carry.

The AD8327 comprises a digitally controlled variable attenuator of 0 dB to 48.16 dB, which is preceded by a low noise, fixed gain buffer and followed by a low distortion, high power amplifier. The AD8327 accepts a differential or single-ended input signal. The output is specified for driving a 75 Ω  load, such as coaxial cable.

Distortion performance of 63 dBc is achieved with an output level up to 60dBmV at 21MHz bandwidth. A key performance and cost advantage of the AD8327 results from the ability to maintain a  constant 75Ω output impedance during Transmit Enable and Transmit Disable conditions. In addition, this device has a sleep mode function that reduces the quiescent current to 5mA.

The AD8327 is packaged in a low-cost 20-lead TSSOP, operates from a single 5 V supply, and has an operational temperature range of 40°C to +85°C.