The AD8321 is a low cost digitally controlled variable gain amplifier optimized for coaxial line driving applications such as cable modems that are designed to the DOCSIS* (upstream) standard.
The AD8321 is a digitally controlled variable‑gain line driver optimized for CATV and cable‑modem applications. It provides a linear-in‑dB gain response over more than 53 dB, supports a 9 V single‑supply, and includes a built‑in SPI‑compatible interface for setting gain in 0.7526 dB steps.
The device drives a 75 Ω load with up to 11 dBm output power while maintaining a constant output impedance during power‑up and power‑down, eliminating the need for an external termination resistor. It offers low distortion, low output noise, and power‑down functionality suitable for upstream DOCSIS modems.
| Gain Range | 52.4 – 54.4 dB |
|---|---|
| Supply Voltage | 9 V single supply |
| Output Impedance | 75 Ω (typical) |
| Bandwidth (‑3 dB) | 120 MHz |
| Input Resistance (single‑ended) | 820 Ω |
| Input Capacitance | 2.0 pF |
| Quiescent Current (Power‑Up) | 82–97 mA |
| Gain Scaling Factor | 0.7526 dB/LSB |
The AD8321 operates from a single 9 V supply.