National Semiconductor has introduced a pair of quad- and dual-channel, digital variable gain amplifiers (DVGA) for wideband radio systems.

In the design of anti-alias filters (AAF) for wideband radio it is found that a range of filter impedance levels, including low impedance levels such as 50ohm, not only simplifies the AAF design, but also improves performance and manufacturability.

These DVGAs are designed to drive a range of load impedances and a low-Z output drive ensures signal fidelity and provides the additional power gain needed when driving low impedance filters.

The LMH6522 and LMH6521 can be used to drive high-speed ADCs, including National’s ADC16DV160 dual 16-bit, 160 MSPS converter.

The LMH6521 can also be used for driving National’s ADC12D500/800RF 12-bit, 500 MSPS/800 MSPS direct RF-sampling ADCs.

By adding the LMX2541 frequency synthesizer and one of National’s family of LMK04800 or LMK04000 clock jitter cleaners, a designer can form a complete signal path.

Target applications include intermediate frequency (IF) sampling receivers, I/Q digital pre-distortion (DPD) signal paths and wide-bandwidth direct-conversion radios used in multi-carrier GSM, TD-SCDMA, W-CDMA and LTE wireless basestations.
 
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