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ADA4500 understanding load capacitance effects


I'm using the ada4500 in a product design and have a questions regarding how load capacitance effects the part.  Could someone explain what exactly figure 37 in the data sheet means?  What is small signal overshoot and how do I apply that graph to an actual load capacitance.  How does that tie into the stability of the amp etc...  I don't understand how to use the information provided in that plot. 

I'm looking at driving a 100pF cap to support ADC input channels and am not sure if I need small series resistors to prevent performance degradation. 

Here is the plot:

  • Hi Robbie, 

    Apologies for the delay.

    From the small signal overshoot vs. load capacitance graph, we see that there is about 40-45% overshoot when the load capacitance is 100pF. Looking at Figure 39 helps to better understand the relationship visually. The observed overshoot below correlates to the figure. Based on this data, the overshoot would get larger as your load capacitance increases. 

    The overshoot in the transient response is indicative of the stability of your system. The higher the overshoot, the likelier it is to go unstable.

    Judging from Figures 37 and 39, you may be teetering on the edge of instability with a 100pF load. It would be best to include some provisions in your design to compensate for this. The article at this link should give you more information on what options you can take. 

    I hope this helps. 


  • Thanks this was helpful!  I ended up putting a 10R in series with the output.