I'm testing the open loop transfer function of an op-amp circuit by following this schematic:
This is my LTspice schematic (keep in mind the actual op-amp circuit itself has been thoroughly checked, but if you think there might be a problem feel free to point it out):
Finally, this is the Bode plot I obtain (this was run on a new installation of LTSspice and no control panel settings were changed):
As you can see there is a single corner frequency and the gain crossover is not reached before 100 MHz. However, I believe that the correct Bode plot should present twk corner frequencies, and should drop to 0 dB before 100 MHz. It should look something like this (this was run on a different computer):
The simulated circuits are identical (except for the wire connecting T10 collector and T9 emitter, which does not produce the second corner frequency), but somehow the plots are different.
UPDATE: I have gone into the standard LTspice library and updated the transistors' capacitances values CJC (Cob) and CJE (Cib) as per the components' datasheets
.model 2N2222 NPN(IS=1E-14 VAF=100 + BF=200 IKF=0.3 XTB=1.5 BR=3 + CJC=8E-12 CJE=30E-12 TR=100E-9 TF=400E-12 + ITF=1 VTF=2 XTF=3 RB=10 RC=.3 RE=.2 Vceo=30 Icrating=800m mfg=NXP) .model 2N2907 PNP(IS=1E-14 VAF=120 + BF=250 IKF=0.3 XTB=1.5 BR=3 + CJC=8E-12 CJE=30E-12 TR=100E-9 TF=400E-12 + ITF=1 VTF=2 XTF=3 RB=10 RC=.3 RE=.2 Vceo=40 Icrating=600m mfg=NXP)
This made no difference to the original simulation and Bode plot. Maybe somebody with a keener eye can notice inconsistencies in the models.
If anybody has any idea as to why this is happening, I would be very glad with your help.