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Newbie level 4
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Hi everyone,
I need to characterize a buffer (OTA rail-to-rail with cascode stage and class AB output stage) but I have not understood how to correctly make the simulation to obtain input and output impedance.
So the amplifier is in feedback configuration and for input impedance I have connected an ac current source (1V) to the input. I also connected a DC source for my operating point. But when I launch an ac simulation and plot voltage at the desired node, this does not work. When I remove the DC source I have an input impedance from Gohms to ohms over the frequency range.
In a datasheet that I need to take as an example, there is only one value so I am a bit confused on how to obtain it and how to make sure it is accurate.
As for the output impedance, I also plan to connect an AC current source but should I keep the loads that I have ? (inductance and RC filter) or characterize the output impedance without any load ? I imagine also that it varies with frequency.
So what is the best method to have these characteristics ?
Thanks
I need to characterize a buffer (OTA rail-to-rail with cascode stage and class AB output stage) but I have not understood how to correctly make the simulation to obtain input and output impedance.
So the amplifier is in feedback configuration and for input impedance I have connected an ac current source (1V) to the input. I also connected a DC source for my operating point. But when I launch an ac simulation and plot voltage at the desired node, this does not work. When I remove the DC source I have an input impedance from Gohms to ohms over the frequency range.
In a datasheet that I need to take as an example, there is only one value so I am a bit confused on how to obtain it and how to make sure it is accurate.
As for the output impedance, I also plan to connect an AC current source but should I keep the loads that I have ? (inductance and RC filter) or characterize the output impedance without any load ? I imagine also that it varies with frequency.
So what is the best method to have these characteristics ?
Thanks