F1200 Low-noise Digital IF VGA with FlatNoise
The F1200 of an IDT is a digitally controlled intermediate frequency differential variable gain amplifier that adjusts the gain either dynamically or as a one-time channel gain setting. The device has extremely low noise figure over the entire gain control range. It is packaged in compact 5×5 Thin QFNs with 200 ohm differential input and output impedances for ease of integration into the receiver lineup with IF frequencies up to 300MHz.
The device has exceptional DNL and INL simplifying digital compensation. It has extremely low Harmonic, IM2, and IM3 distortion that is necessary to drive an ADC directly in an IF sub-sampling application. The F1200 acts to enhance system SNR when VGA gain is reduced. The F1200 noise figure (NF) degrades only slightly (NF slope ~ -0.16 dB/dB) over a 13 dB control range while holding the output IP3 approximately constant. The resultant improvement in noise can enhance the system SNR up to 2 decibels at low gain settings relative to a standard VGA.
This design is used in either transmitter or receiver to add an adjustable gain element to the signal chain by increasing or decreasing the attenuation value. Other applications include base station, diversity receivers, digital pre-distortion, μ–wave point-to-point radios and public safety receivers.
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