AD8320

The AD8320 is a digitally controlled variable gain amplifier suitable for coaxial line drive applications.An 8-bit serial word determines the required output gain over a 36 dB range (256 gain levels).The AD8320 provides linear gain response.

The AD8320 consists of a digitally controlled variable attenuator with a 0dB to 36dB crossover preceded by a low noise, fixed gain buffer followed by a low distortion high power amplifier.The AD8320 has a 220 ohm input impedance and accepts single-ended input signals with specified analog input levels up to 0.310 V pp. Despite the capabilities of the AD8320, the output is intended to drive a 75 ohm load, as is the case with coaxial cable driving other loads.At 42 MHz, the output level reaches 57 dBc at 12 dBm (3.1 V pp), while a distortion of 46dBc is achieved at an output level of 18 dBm (6.2 V pp).

A key performance and cost advantage of the AD8320 is its ability to maintain a constant 75-ohm output impedance during power-up and power-down conditions.This eliminates the need for an external 75-ohm backend, resulting in twice the effective output voltage compared to a standard op amp.Additionally, on-chip 75-ohm termination results in low glitch output during power-down and power-up transitions, eliminating the need for external switches.

The AD8320 is packaged in a 20-lead SOIC, operates from a single +5 V to +12 V supply, and operates over the -40°C to +85°C temperature range.

This product is available as an evaluation board and can be ordered using the following product number: AD8320-EB.The schematic and layout of this evaluation board are included in the product data sheet.