Low noise fully differential 1.6-GHz buffer drives 50-Ohm load

August 16, 2012 // By Paul Buckley
Linear Technology has unveiled a fully differential buffer amplifier with 1.5 nV/√Hz output-referred noise. The LTC6417 is capable of driving a differential 50 Ohm load and is optimized for driving 14- and 16-bit pipeline ADCs.

The device can be DC- or AC-coupled at its inputs, and achieves excellent distortion performance for signals up to and beyond 600 MHz. At 140 MHz, OIP3 is 46 dBm, and HD3 is -69 dBc with 2.4 VP-P output swing into a 50 Ohm load.

In addition to its outstanding performance specifications, the LTC6417 includes several features designed to simplify interfacing with ADCs. The LTC6417 is configured internally as a unity gain buffer. Because its input impedance is 18.5 kOhm, additional gain can be achieved by applying a 1:4 or 1:8 transformer at the inputs. Its low impedance output helps manage the capacitive charge injection common to pipeline ADCs. Fast output clamps can be programmed with a single pin to prevent ADC overrange conditions. An overrange pin signals when the clamps limit the output voltage. An output common mode pin makes it easy to match the LTC6417 output swing to the input range of the ADC.

The LTC6417 operates from a single 5 V supply. A PWRADJ pin enables the designer to trade off power consumption for HD3 performance. The feature dynamically lowers supply current from 123 mA to 74 mA, and a shutdown mode further reduces current consumption to 24 mA.

Availability and Pricing

The LTC6417 is available in a 3 mm x 4 mm 20-lead QFN package with an easy to use flow-through pinout. It is fully specified for 0 to 70°C and -40 to 105°C (case temperature) operation ranges. Pricing starts at $3.89 each in 1,000 piece quantities.

More information about the LTC6417 differential buffer amplifier at www.linear.com/product/LTC6417