Differential Amplifiers Optimized For Driving High-Speed ADCs

A pair of differential amplifiers from Analog Devices Inc. target analog-to-digital-converter (ADC) driver applications, combining the low noise and distortion levels required to drive the high-speed ADCs found in today's wireless infrastructure and instrumentation equipment. The ADA4937-1 is well-suited for single 3- to 5-V power supplies, achieving a distortion of −120/−102 dBc at 10 MHz, −98/−100 dBc at 40 MHz, and −84/−90 dBc at 70 MHz. The ADA4938-1 works over a 5- to 10-V range in dual-supply applications and achieves distortion of −112/−108 dBc at 10 MHz, −96/−93 dBc at 30 MHz, and −79/−81 dBc at 50 MHz. The devices’ ultra-low distortion results from the use of ADI’s XFCB-3, a proprietary and specialized silicon-germanium (SiGe) silicon-on-insulator process technology, notes the company.

The devices operate from dc to 100 MHz. The ADA4937-1 has 16-bit performance up to 40 MHz, 14-bit performance to 70 MHz, and 12-bit performance to 100 MHz. The devices also feature an internal common-mode feedback architecture, which allows the output common-mode voltage to be controlled by an externally applied voltage. This bridges any gap between the output range of the component before the ADC and the input range of the ADC, eliminating the need for ac coupling and making the drivers well-suited for dc-coupled applications, such as data-acquisition instruments and baseband communications systems. The drivers come in 3- by 3-mm lead-frame chip-scale packages and are specified over an operating temperature range of 0°C to 85°C.