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ADC driver touts distortion performance, low power

Posted: 16 Jun 2008 ?? ?Print Version ?Bookmark and Share

Keywords:ADC driver? differential amplifiers? baseband signal processing?


Analog Devices Inc. has extended its family of differential amplifiers by introducing a new device with the industry's best distortion performance at the lowest power consumption for engineers who need maximum performance when driving high-resolution ADCs in communications infrastructure, instrumentation and other high-speed equipment. Optimized to drive today's high-performance 14bit and 16bit converters, the ADA4939 differential amplifier consumes less than 120mW of power on a single 3.3V supply, while achieving 82dB SFDR at 70MHz. The differential amplifier is available in one- and two-channel versions that can drive ADCs with resolutions up to 16bits, such as ADI's AD9460 and AD9461 ADCs, and can drive low-power, 14bit ADCs, such as ADI's AD9246.

The ADA4939 can be used in either differential-to-differential or single-ended-to-differential configurations. An internal common-mode feedback loop allows the user to independently adjust the ADA4939 output common-mode level to match the input common mode voltage of the ADC, and at the same time achieve exceptional output balance and suppression of even-order harmonics.

The ADA4939 is well suited to communications applications, such as cellular base stations using low intermediate frequency and baseband signal processing at frequencies up to 100MHz, and where 14bit and 16bit accuracy is required. The two-channel version, the ADA4939-2, is suitable for driving dual ADCs used in I/Q demodulation schemes. It offers low crosstalk of -80dB at 100MHz while providing gain and phase matching.

The ADA4939 is fabricated using ADI's proprietary SiGe complementary bipolar process, enabling it to achieve very low levels of distortion with an input voltage noise of 2.3nV/rt Hz, as well as -3dB bandwidth of 1.4GHz (G=+2) and a slew rate of 5,000V/?S. The ADA4939 is specified to operate over the -40 C to 105C temperature range for both 3.3V and 5V operation.

The ADA4939-1 and ADA4939-2 are available now in production quantities. The ADA4939-1 is housed in a Pb-free, 3mm x 3mm 16-lead LFCSP, and the two-channel ADA4939-2 comes in a 4mm x 4mm 24-lead LFCSP. The ADA4939-1 is priced at $3.79 each and the ADA4939-2 is priced at $5.69 each, both in 1,000-unit quantities.

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