ADL5201 - Output impedance and Gain


Does the gain of ADL5201 dependent on the output Load? We are planning to use another Differential amplifier (AD8352) at the output of ADL5201 to provide Multi-stage gain. AD8352 has high input impedance, so it should be possible for ADL5201 to drive the AD8352 directly, right? Does the output gain vary to a High impedance load? If it so, Can we just add 150 ohm resistance at parallel to the input of the AD8352, so that ADL5201 sees 150 ohm load and ensure gain does not vary? In this case should also ensure PCB traces have differential  150 ohm impedance?

Can the input to the ADL5201 be single ended? We do not want to use any transformers at the input. And can we add  75 ohm impedance at the input of the VGA and thus provide 50 ohm load to the preceding device without needing any Impedance matching Transformer?

  • 0
    •  Analog Employees 
    on Oct 2, 2012 4:46 PM

    The gain of the ADL5201 is load dependant. This is discussed in the circuit description section of the ADL5201 datasheet. (pg 17) The equations necessary to calculate the new gain based on load impedance are listed in the OUTPUT AMPLIFIER section. (pg 17)

    When using the ADL5201 optimal distortion is achieved wnen driving a 150 ohm load. Placing a 158 ohm resistor in shunt with the AD8352 will present a 150 ohm impedance to the ADL5201.

    It is possible to drive the ADL5201 input from a single ended 50 ohm source without transformers. The attached schematic shows the required componets to create the singled ended input.

  • 0
    •  Analog Employees 
    on Aug 2, 2018 4:40 PM
    This question has been assumed as answered either offline via email or with a multi-part answer. This question has now been closed out. If you have an inquiry related to this topic please post a new question in the applicable product forum.

    Thank you,
    EZ Admin