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AD8310 Loading

Hello,

Does the AD8310 have to be loaded to work correctly?  It seems to indicate in the datasheet that it does but the schematic for Eval board in the datasheet shows the load resistance and load capacitance as normally open.  My current design has a zero drift op-amp (OPA388) as a unity gain buffer with an RC lowpass filter on its output between the AD8310 and an ADC, .  Do I need to put a load resistor on the output of the AD8310? The datasheet says minimum load resistance of 100 ohms.  Is that the recommended value?  Can you give me a little more explanation of that?  I understand that the output can drive 25mA and the output voltage voltage goes to 2.5V at max input voltage, so that is 100 ohm, but it seems strange to me that you would want to drive it a full load current capabilities.  If I put 200 ohms for load, what would I be giving up?

  • Hi,

    I moved your question about AD8310 to RF and Microwave community.
    Someone here should be able to assist you.

    Thanks and regards!

  • Hi trecb,

    100 Ohm is the minimum resistor value of external loading.  Higher resistor values approaching infinity are fine, or no resistor is OK. The output is low-impedance, thanks to the on-chip buffer amplifier. If loaded with 200 Ohms, current consumption will appear to increase, since the extra output source current comes from the VPOS pin. For example, expect current consumption to increase by 10mA when driven such that VOUT = 2V.   -Bruce H.