Simulating PA supply pin input impedance

[viperpaki007]

Hi,

Can anybody tell how i can simulate class-B PA input impedance at DC-power supply node.

regards

 

[erikl]

... input impedance at DC-power supply node.

I'd try it this way:

1. Connect the power supply to the PA power supply input via a huge series inductance (e.g. 100H), to get rid of the power supply's impedance
2. adjust the operating point and input/output behaviour of your PA to the conditions at which you want its power input impedance
3. insert a unit (1A) ac source in parallel to the PA's power supply input node
4. run an ac analysis
5. plot the ac voltage at this power supply node vs. frequency.

This is the input impedance at this node (V≙Ω) at the adjusted I/O conditions of your PA, because the parallel impedance of the power supply is much larger due to the serial inductance, at least for frequencies of your interest.