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  • F1240 Low-noise Dual IF VGA with FlatNoise(TM)

  • Created: Nov 10, 2015

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The IDT F1240NBGI device is a dual intermediate frequency (IF) digital variable gain amplifier (VGA) that offers better performance in rejecting noise and minimizing distortion than the current VGA devices available today. It is packaged in a compact 5x5 thin QFN with 200Ω differential input and output impedances for ease of integration into the receiver lineup. The device has a maximum gain of 20dB with 31.5dB gain control range. The gain is controlled through a 6-bit codeword with 0.5dB gain steps. This device requires 5VDC supply voltage and 80mA supply current per channel.

The F1240NBGI device used in this reference design controls the gain of two IF signal inputs ranging from 10 to 500MHz. It changes the gain of an IF signal in a 31.5dB gain control range. The input signals are inserted at SMA jacks J1 and J3 and the outputs are taken at SMA jacks J4 and J5. The gain setting of the device can be adjusted through parallel or series mode. In parallel mode, the gain for channels A and B is controlled by pulling pins GA0-5 and GB0-5 to HIGH or LOW. In serial mode, the gain is set through pin CLK, pin CSb, and pin DATA. The CLK pin is used for clocking while the pin CSb is used to select which channel will be programmed. The DATA pin is where the gain setting for channel A and B will be inputted. To select the mode for gain setting, pull VMODE pin to HIGH or LOW. When VMODE pin is pulled LOW, the mode is serial, and if it is pulled HIGH, the mode is parallel. Each channel of this device can be enabled or disabled by pulling pins STYB_A and STYB_B to HIGH or LOW.

The F1240NBGI IF VGA improves system signal-to-noise ratio (SNR) even at lower gain settings. Through IDT’s FlatNoise technology, both output third order intercept point and noise figure are maintained virtually flat while gain is backed off, which is also advantageous to 2G/3G/4G Multi-Carrier IF sampling receivers. This reference design is ideal for applications that require high SNR.



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