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Biasing an LDO Regulator to Measure Small Signal Noise Input to Output

Question asked by cracraft on Sep 22, 2014
I would like to determine the level of small signal noise coupling on a low-drop-out regulator in a power distribution network design I am testing.  I assumed I could set this up similar to a amplifier measurement except that I need to bias the input signal a 3.3V input voltage and protect the port input from the 1.2V output of the regulator.  My N5242A has the bias tee option, but I have never used it.  In the past I have only ever used my VNA for purely passive measurements.

My first question is how do I set up this measurement while protecting my VNA from damage?

My second question is how sensitive are the VNA inputs to DC voltages?  I always learned spectrum analyzer front-ends were extremely sensitive to DC inputs, and as a result, I don't think I have ever operated a spectrum analyzer without a DC block on the input.  +As an extra question, is that DC sensitivity still true of spectrum analyzers like the N9030A we purchased last year?+

I have at my disposal attenuators, DC blocks, tees (not bias tees unfortunately), and power splitters.