I have problems to simulate negative psrr in two stage opamp... If i consider an ac Vss in series with a dc VSS, if opamp is configured as buffer with V+ to ground, i should have Vout/Vss=1/ Psrr-, so Psrr-=Vss/Vout.....is this right? I've simulated this configuration in spice with dc VSS=2V and ac Vss=0.1V, so psrr- should be Vss(=0.1V)/Vout... My problem is bode plot of Vss/Vout: arg[Vss/Vout] has higher values at higher frequency and this is not possible: what's wrong? Using the same method with psrr+ i have the right bode plot, so i think i've done some error in plotting....Can you help me? Thanks in advance
Negative PSRR in two stage opamp
Sep 25, 2008
3 Replies
schrieb im Newsbeitrag news: snipped-for-privacy@59g2000hsb.googlegroups.com...
Hello,
Is there any comment in the model that the PSRR is modeled? If not, the simulation will be useless. Please show the model text.
Best regards, Helmut
thanks for the answer... i don't have opamp macromodel because i've done the same two stage opamp used in this link: users.ece.gatech.edu/~pallen/Academic/ECE_6412/Spring_2003/L180- PSRR-2UP.pdf I've tried to use the same method to calculate positive psrr and negative psrr, but for negtive prss i have obtained this picture
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i don't understand the picture, because phase shoud descrease as frequency increases and not the contrary.... For positive psrr using the same method i have a correct bode plot... What's wrong? thanks
schrieb im Newsbeitrag news: snipped-for-privacy@c58g2000hsc.googlegroups.com...
Hello,
This may be just a question how you have polarized your AC-source in series with the supply voltage source.
Taking care of phase in a PSSR simulation is nonsense in my opinion.
Best regards, Helmut
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