If diff pair is loaded by current mirror and your signal path going through positive input and is mirroring on the load I'm not sure if this zero should be always beyond UGF.
Just ordinary PMOS loads (i.e., current sources)...
It could enlarge Cgd anyway. Measure it by simulation.Why to Cgd? They add caps to the output node (parallel to Cdb) but not back to the input (and hence not Cgd)?
The simplest way to measure a node's total capacitance is to inject a unit current (1A) into this node, run an ac analysis and plot the node's voltage vs. frequency.Also,any idea how to measure the actual cap between two nodes (Cgd)? Captab of DC analysis shows 0F
@erikl: Thanks! But is there also a way to measure capacitance between two nodes? As would be required for this case (the zero)?
I really have no idea what I can trust. Why is this all so inconsistent and wrong?
N0.xmmaster.csdext:cap,475.9E-18
N0.xmmaster.m1:beff,21.98E-3
N0.xmmaster.m1:cbb,2.734E-15
N0.xmmaster.m1:cbd,803.0E-18
N0.xmmaster.m1:cbg,1.008E-15
N0.xmmaster.m1:cbs,923.4E-18
N0.xmmaster.m1:cdb,956.7E-18
N0.xmmaster.m1:cdd,3.334E-15
N0.xmmaster.m1:cdg,4.700E-15
N0.xmmaster.m1:cds,-2.323E-15
N0.xmmaster.m1:cgb,577.4E-18
N0.xmmaster.m1:cgd,2.416E-15
N0.xmmaster.m1:cgg,11.89E-15
N0.xmmaster.m1:cgs,8.895E-15
N0.xmmaster.m1:csb,1.200E-15
N0.xmmaster.m1:csd,114.6E-18
N0.xmmaster.m1:csg,6.180E-15
N0.xmmaster.m1:css,7.495E-15
N0.xmmaster.m1:delvg_op,2.706E-3
N0.xmmaster.m1:eg_op,1.124
N0.xmmaster.m1:fug,23.75E9
N0.xmmaster.m1:gds,29.38E-6
N0.xmmaster.m1:gm,1.774E-3
N0.xmmaster.m1:gmb,117.5E-6
N0.xmmaster.m1:gmoverid,17.74
N0.xmmaster.m1:ibe,0.000
N0.xmmaster.m1:idb,0.000
N0.xmmaster.m1:ide,100.0E-6
N0.xmmaster.m1:ids,100.0E-6
N0.xmmaster.m1:ige,13.97E-12
N0.xmmaster.m1:isb,0.000
N0.xmmaster.m1:ise,-100.0E-6
N0.xmmaster.m1:isnoisy,1.000
N0.xmmaster.m1:neff,1.045
N0.xmmaster.m1:ni_op,14.39E15
N0.xmmaster.m1:phit1_op,27.73E-3
N0.xmmaster.m1:phit_op,25.86E-3
N0.xmmaster.m1:pwr,33.00E-6
N0.xmmaster.m1:qgde_op,0.000
N0.xmmaster.m1:qgse_op,0.000
N0.xmmaster.m1:rgate,0.000
N0.xmmaster.m1:rout,34.04E3
N0.xmmaster.m1:self_gain,60.38
N0.xmmaster.m1:vbx_op,-670.6E-3
N0.xmmaster.m1:vds,330.0E-3
N0.xmmaster.m1:vdss,132.2E-3
N0.xmmaster.m1:vdst,330.0E-3
N0.xmmaster.m1:vearly,3.405
N0.xmmaster.m1:vfb_op,-187.6E-3
N0.xmmaster.m1:vfbb_low_op,485.0E-3
N0.xmmaster.m1:vfbb_op,517.5E-3
N0.xmmaster.m1:vgs,530.0E-3
N0.xmmaster.m1:vgst,530.0E-3
N0.xmmaster.m1:vgt,95.40E-3
N0.xmmaster.m1:vsat_marg,197.8E-3
N0.xmmaster.m1:vsb,0.000
N0.xmmaster.m1:vsbt,0.000
N0.xmmaster.m1:vth,434.6E-3
N0.xmmaster.m1:vto,437.3E-3
N0.xmmaster.m1:vts,437.3E-3
N0.xmmaster.rg:i,13.97E-12
N0.xmmaster.rg:pwr,14.15E-21
N0.xmmaster.rg:res,72.49
N0.xmmaster.rg:v,1.013E-9
N0.xmmaster.gi : 0:Fixed,0.000
N0.xmmaster.gi : 0:Total,0.000
N0.xmmaster.gi : 0:Variable,0.000
N0.xmmaster.gi : N0.xmmaster.gi:Fixed,0.000
N0.xmmaster.gi : N0.xmmaster.gi:Total,11.89E-15
N0.xmmaster.gi : N0.xmmaster.gi:Variable,11.89E-15
N0.xmmaster.gi : net5:Fixed,9.472E-15
N0.xmmaster.gi : net5:Total,9.472E-15
N0.xmmaster.gi : net5:Variable,0.000
N0.xmmaster.gi : vip:Fixed,0.000
N0.xmmaster.gi : vip:Total,0.000
N0.xmmaster.gi : vip:Variable,0.000
N0.xmmaster.gi : vom:Fixed,2.416E-15
N0.xmmaster.gi : vom:Total,2.416E-15
N0.xmmaster.gi : vom:Variable,0.000
N1.xmmaster.gi : 0:Fixed,0.000
N1.xmmaster.gi : 0:Total,0.000
N1.xmmaster.gi : 0:Variable,0.000
N1.xmmaster.gi : N1.xmmaster.gi:Fixed,0.000
N1.xmmaster.gi : N1.xmmaster.gi:Total,11.89E-15
N1.xmmaster.gi : N1.xmmaster.gi:Variable,11.89E-15
N1.xmmaster.gi : net5:Fixed,9.472E-15
N1.xmmaster.gi : net5:Total,9.472E-15
N1.xmmaster.gi : net5:Variable,0.000
N1.xmmaster.gi : vim:Fixed,0.000
N1.xmmaster.gi : vim:Total,0.000
N1.xmmaster.gi : vim:Variable,0.000
N1.xmmaster.gi : vop:Fixed,2.416E-15
N1.xmmaster.gi : vop:Total,2.416E-15
N1.xmmaster.gi : vop:Variable,0.000
/net5 : 0:Fixed,0.000
/net5 : 0:Total,0.000
/net5 : 0:Variable,0.000
net5 : N0.xmmaster.gi:Fixed,7.188E-15
net5 : N0.xmmaster.gi:Total,7.188E-15
net5 : N0.xmmaster.gi:Variable,0.000
net5 : N1.xmmaster.gi:Fixed,7.188E-15
net5 : N1.xmmaster.gi:Total,7.188E-15
net5 : N1.xmmaster.gi:Variable,0.000
/net5 : net5:Fixed,951.8E-18
/net5 : net5:Total,17.16E-15
/net5 : net5:Variable,16.21E-15
/net5 : net06:Fixed,0.000
/net5 : net06:Total,0.000
/net5 : net06:Variable,0.000
/net5 : net09:Fixed,0.000
/net5 : net09:Total,0.000
/net5 : net09:Variable,0.000
/net5 : vom:Fixed,917.7E-18
/net5 : vom:Total,1.394E-15
/net5 : vom:Variable,475.9E-18
/net5 : vop:Fixed,917.7E-18
/net5 : vop:Total,1.394E-15
/net5 : vop:Variable,475.9E-18
/net06 : 0:Fixed,0.000
/net06 : 0:Total,0.000
/net06 : 0:Variable,0.000
/net06 : net06:Fixed,0.000
/net06 : net06:Total,0.000
/net06 : net06:Variable,0.000
/net06 : vom:Fixed,0.000
/net06 : vom:Total,0.000
/net06 : vom:Variable,0.000
/net06 : vop:Fixed,0.000
/net06 : vop:Total,0.000
/net06 : vop:Variable,0.000
/net08 : 0:Fixed,0.000
/net08 : 0:Total,0.000
/net08 : 0:Variable,0.000
/net08 : net08:Fixed,0.000
/net08 : net08:Total,0.000
/net08 : net08:Variable,0.000
/net09 : 0:Fixed,0.000
/net09 : 0:Total,0.000
/net09 : 0:Variable,0.000
/net09 : net09:Fixed,0.000
/net09 : net09:Total,0.000
/net09 : net09:Variable,0.000
/vdd! : 0:Fixed,0.000
/vdd! : 0:Total,0.000
/vdd! : 0:Variable,0.000
/vdd! : vdd!:Fixed,0.000
/vdd! : vdd!:Total,0.000
/vdd! : vdd!:Variable,0.000
/vic : 0:Fixed,0.000
/vic : 0:Total,0.000
/vic : 0:Variable,0.000
/vic : vic:Fixed,0.000
/vic : vic:Total,0.000
/vic : vic:Variable,0.000
/vic : vim:Fixed,0.000
/vic : vim:Total,0.000
/vic : vim:Variable,0.000
/vic : vip:Fixed,0.000
/vic : vip:Total,0.000
/vic : vip:Variable,0.000
/vid : 0:Fixed,0.000
/vid : 0:Total,0.000
/vid : 0:Variable,0.000
/vid : vid:Fixed,0.000
/vid : vid:Total,0.000
/vid : vid:Variable,0.000
/vim : 0:Fixed,0.000
/vim : 0:Total,0.000
/vim : 0:Variable,0.000
vim : N1.xmmaster.gi:Fixed,0.000
vim : N1.xmmaster.gi:Total,0.000
vim : N1.xmmaster.gi:Variable,0.000
/vim : vic:Fixed,0.000
/vim : vic:Total,0.000
/vim : vic:Variable,0.000
/vim : vim:Fixed,0.000
/vim : vim:Total,0.000
/vim : vim:Variable,0.000
/vim : vom:Fixed,0.000
/vim : vom:Total,0.000
/vim : vom:Variable,0.000
/vip : 0:Fixed,0.000
/vip : 0:Total,0.000
/vip : 0:Variable,0.000
vip : N0.xmmaster.gi:Fixed,0.000
vip : N0.xmmaster.gi:Total,0.000
vip : N0.xmmaster.gi:Variable,0.000
/vip : vic:Fixed,0.000
/vip : vic:Total,0.000
/vip : vic:Variable,0.000
/vip : vip:Fixed,0.000
/vip : vip:Total,0.000
/vip : vip:Variable,0.000
/vip : vop:Fixed,0.000
/vip : vop:Total,0.000
/vip : vop:Variable,0.000
/voc : 0:Fixed,0.000
/voc : 0:Total,0.000
/voc : 0:Variable,0.000
/voc : voc:Fixed,0.000
/voc : voc:Total,0.000
/voc : voc:Variable,0.000
/voc : vom:Fixed,0.000
/voc : vom:Total,0.000
/voc : vom:Variable,0.000
/voc : vop:Fixed,0.000
/voc : vop:Total,0.000
/voc : vop:Variable,0.000
/vod : 0:Fixed,0.000
/vod : 0:Total,0.000
/vod : 0:Variable,0.000
/vod : vod:Fixed,0.000
/vod : vod:Total,0.000
/vod : vod:Variable,0.000
/vom : 0:Fixed,0.000
/vom : 0:Total,0.000
/vom : 0:Variable,0.000
vom : N0.xmmaster.gi:Fixed,4.700E-15
vom : N0.xmmaster.gi:Total,4.700E-15
vom : N0.xmmaster.gi:Variable,0.000
/vom : net5:Fixed,-1.366E-15
/vom : net5:Total,-890.3E-18
/vom : net5:Variable,475.9E-18
/vom : net06:Fixed,0.000
/vom : net06:Total,0.000
/vom : net06:Variable,0.000
/vom : vim:Fixed,0.000
/vom : vim:Total,0.000
/vom : vim:Variable,0.000
/vom : voc:Fixed,0.000
/vom : voc:Total,0.000
/vom : voc:Variable,0.000
/vom : vom:Fixed,475.9E-18
/vom : vom:Total,3.810E-15
/vom : vom:Variable,3.334E-15
/vop : 0:Fixed,0.000
/vop : 0:Total,0.000
/vop : 0:Variable,0.000
vop : N1.xmmaster.gi:Fixed,4.700E-15
vop : N1.xmmaster.gi:Total,4.700E-15
vop : N1.xmmaster.gi:Variable,0.000
/vop : net5:Fixed,-1.366E-15
/vop : net5:Total,-890.3E-18
/vop : net5:Variable,475.9E-18
/vop : net06:Fixed,0.000
/vop : net06:Total,0.000
/vop : net06:Variable,0.000
/vop : vip:Fixed,0.000
/vop : vip:Total,0.000
/vop : vip:Variable,0.000
/vop : voc:Fixed,0.000
/vop : voc:Total,0.000
/vop : voc:Variable,0.000
/vop : vop:Fixed,475.9E-18
/vop : vop:Total,3.810E-15
/vop : vop:Variable,3.334E-15
DC simulation time: CPU = 1 ms, elapsed = 346.899 us.
Poles (Hz)
Real Imaginary Qfactor
1 -1.13249e+09 0.00000e+00 5.00000e-01
2 -2.67090e+11 0.00000e+00 5.00000e-01
Zeros (Hz)
at V(vop,vom)/V3
Real Imaginary Qfactor
1 6.00631e+10 0.00000e+00 -5.00000e-01
Constant factor = 1.91063e+12
DC gain = 6.03826e+01
Actually not, sorry!So, can you spot anything I am doing wrong?
I don't feel I can even start thinking about more complicated circuits when even single transistor circuits are unpredictable and inconsistent
I don't think it makes much sense to analyze ideal circuits - better try and design real circuits.
Ac analyze the open loop circuits, plot the Bode diagrams and check for gain, stability and phase margin, perhaps check with PZ analysis. Then comes closed loop - feedback changes quite a lot - and then the not quite well predictable parasitics from extracted layout.
1.) Do I apply it (see screenshots) correctly for differential circuit?
I could estimate the cout part to a value of ≈4.25 fF (using the 34kΩ-3dB frequency point 1.1GHz, where both parts rout & cout have the same value (34kΩ) and are added quadratically to 24kΩ (34kΩ - 3dB)). For the cout calculation, the impedance of 34kΩ must be used, of course.
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