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ADA4960 Gain Setting Resistor not working

Question asked by timothy.starr on Feb 2, 2012
Latest reply on Feb 9, 2012 by Zoltan


I have a board with an ADA4960 amplifier that is used to amplify a signal between 1 -2 GHz before going into a high-speed ADC.  I am having a problem with the amplifier not providing the correct amount of gain given the value of the gain setting resistor.  The part is supposed to provide an 18 dB gain with a 0 ohm resistor, but I’m only seeing about 8 dB.  I’ve tried changing the gain setting resistor value to 50 Ohms, but it only makes a slight difference (1-2 dB lower) in the gain.  I’ve also tried replacing the chip, but no difference in performance.    The input is AC coupled with an amplitude of 150mVp-p and the load is 100 Ohms resistive. Power supply is 5V. Why can;t I get 18dB og gain?


-Tim Starr on behalf of RS@ML