how to measure the rout of the OP Amplifer

[wifish2009]

how to measure rload

hi all

I want to know how to simulate the rout of the OP while using spectre.

Can you tell me how to do this in detail.



Thank you very much!!!

 

[saro_k_82]

what is the rout of current amplifier

Connect a current source(idc) as the load (in addition to the actual load) with zero dc current, ac mag=1 and run ac analysis. Plot the output ac magnitude to get the output impedance.

 

[LvW]

Connect a current source(idc) as the load (in addition to the actual load) with zero dc current, ac mag=1 and run ac analysis. Plot the output ac magnitude to get the output impedance.

Why "in addition to the actual load". In this case, you get a combined output impedance (rout||Rload). It´s quite logical to disconnect the load !

 

[saro_k_82]

Why "in addition to the actual load". In this case, you get a combined output impedance (rout||Rload). It´s quite logical to disconnect the load !

1. In most of the amplifier applications the load is an integral component for the stability of the loop, simulating without the load can provide misleading results. It can be done without the load only for a generic amplifier designed expecting a variety of loads.
2. The output impedance is required to see the amount of voltage change for a load current change., simulating for it without the load would not provide what you are really looking for.

 

[LvW]

1. In most of the amplifier applications the load is an integral component for the stability of the loop, simulating without the load can provide misleading results. It can be done without the load only for a generic amplifier designed expecting a variety of loads.
2. The output impedance is required to see the amount of voltage change for a load current change., simulating for it without the load would not provide what you are really looking for.

Well, of course I agree to you.
However, wifish2009 has asked for the "output impedance of the OP".
And, in this case, for my understanding the question was related solely to the opamp IC without any external circuitry. Otherwise one should ask for the output impedance of an amplifier built with an opamp as an active unit..