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ADA4950-1/ capacitance load query

Hi,

We do have a catheter cable length of 2.4 meter , trying to understand if the amplifier ADA4950-1 will be able to drive the same or not?

We have set this for a gain of 2. The input level from the FPGA is driven as 2.4V p-p, output of the ADA4950-1 is seen as 4.8V p-p.

There is a change in rise time of the signal (20Mhz burst clocks) that are transmitted via cable!

Can you share the output capacitance driving capacity for the part ADA4950-1.

  • Hi,

    For a voltage feedback (VF) op amp, capacitive load drive capability increases proportionally with gain. This means that a VF op amp that can safely drive a 100-pF capacitance at unity gain should be able to drive a 1000-pF capacitance at a gain of 10. This article is a good reference to read for opamp capacitive loading.

    You can check Figure 18 and 46 plots in the ADA4950 datasheet to give you idea on ADA4950 response with various capacitive loads. The plots are in Gain of 1. For a Gain of 2, a 2.7pF capacitive load that can be safely driven at Gain of 1 would increase proportionally to 5.4pF.