I would like to use the ADL5565 as a differential amplifier having differential input and single output at 5 GHz.
Is it possible to do this?
In this case what is the gain of the circuit?
To use the ADL5565 in a differential-to-single-ended conversion application, you can use one output for the desired signal, and terminate the other side with the same load impedance (e.g., 100 ohm each side). The voltage gain will be exactly one half (6 dB lower) of that when the output signal is taken differentially, since each side will have the same amplitude and 180 deg. out of phase. Additionally, even order distortion will be 20-30 dB worse on the single-ended output, and the common-mode noise will come straight through without cancellation as in the differential case (not sure how much worse).
If the application does not to respond down to DC, It will be much better to use a balun to transform the differential outputs into single ended. For example, to drive a single-ended 50-ohm load, a series 20-ohm resistor can be added to each output pin to provide a 50-ohm output impedance, and the balun's output will be ready to drive the 50-ohm load (please see attached circuit).
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