当输入PMOS对管栅极电压低于1.5V时全差分放大器正负输出均跳变至0V
放大器使用单端转双端电路测试，测试电路如下图所示：
红圈内为芯片内部的全差分放大器，CF1、CF2、RF1、RF2、SW1、SW2集成在芯片内部，本来打算作为跨阻放大器读出一个电容传感器的信号，在这个测试电路里这些元件对测试结果影响不大。
首先可以排除共模反馈电路的影响，因为输出共模电压设置为不同值时正负输出仍有可能同时跳变至0V。例如V1=1.5V，V2减小至1.4V左右时输出跳变至0V；当V1=1.9V，V2减小0.9V左右时输出跳变至0V，跳变发生以前输出信号的共模电压基本正确。
我做了不少试验最终总结出规律，即输入管栅极电压低于1.5V左右时输出就会跳变至0V，测量发现此时放大器的静态电流增加了300uA左右。
除增加了共模反馈电路以及将miller补偿电容位置由MN0、MN1漏极移至源极以外，该全差分放大器与芯片内部的单端放大器结构相同，且参数也基本相同，单端放大器工作均正常。
另附V1=V2=1.5V时仿真得到的放大器内部各管参数如下。由于放大器内部的R1、R2设小了点，导致MN3、MN15、MP3、MP4的过驱动电压较低，我做FIB后使用软针把VB3增加200mV、VB1减少200mV以后仍然存在上述现象：
subcktxi5.xmn7xi5.xmn5xi5.xmn10
element54:m055:m056:m0
model54:nmos_3p3 55:nmos_3p3 56:nmos_3p3
regionSaturatiSaturatiSaturati
id401.9565u399.1468u42.2597u
ibs0.0.-11.2610a
ibd-14.7313p-42.5205p-28.1225p
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vds1.46631.53261.5322
vbs0.0.-548.8877m
vth625.4655m625.4655m819.0732m
vdsat276.2309m275.2293m143.9517m
vod339.3291m337.9048m132.0392m
beta8.4777m8.4786m4.0095m
gam eff678.0000m678.0000m678.0000m
gm2.1435m2.1366m463.3134u
gds3.6453u3.5503u1.2565u
gmb711.0916u708.9481u126.5631u
cdtot69.5542f68.5671f14.2087f
cgtot616.0526f615.4216f70.7657f
cstot490.1482f490.0745f67.9997f
cbtot341.1842f340.7652f52.6117f
cgs550.6203f550.4342f60.9859f
cgd19.1658f18.6427f4.1713f
subcktxi5.xmn1xi5.xmn0xi5.xmn3xi5.xmn15xi5.xmn17
element57:m058:m059:m060:m061:m0
model57:nmos_3p3 58:nmos_3p3 59:nmos_3p3 60:nmos_3p3 61:nmos_3p3
regionSaturatiSaturatiLinearLinearSaturati
id60.0377u60.0377u124.7360u124.7361u20.3794u
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vth747.8014m747.8003m625.4655m625.4655m815.0392m
vdsat106.6158m106.6187m270.4055m270.4055m281.4837m
vod78.1808m78.1859m331.0440m331.0440m314.9155m
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gam eff678.0000m678.0000m678.0000m678.0000m678.0000m
gm836.7625u836.7567u670.0801u670.0815u117.3757u
gds2.9410u2.9445u19.8205u19.8191u131.2311n
gmb248.0874u248.0861u223.1575u223.1579u30.4891u
cdtot64.9471f64.9643f39.8381f39.8378f11.3330f
cgtot200.0838f200.0908f211.3310f211.3309f129.0100f
cstot180.1785f180.1803f174.1719f174.1719f95.5659f
cbtot166.5533f166.5657f134.1885f134.1884f58.2000f
cgs160.4497f160.4523f183.5252f183.5252f117.2564f
cgd18.0832f18.0882f13.2732f13.2730f2.3420f
subcktxi5.xmn9xi5.xmn19xi5.xmn12xi5.xmn16xi5.xmn20
element62:m063:m064:m065:m066:m0
model62:nmos_3p3 63:nmos_3p3 64:nmos_3p3 65:nmos_3p3 66:nmos_3p3
regionSaturatiLinearSaturatiSaturatiSaturati
id21.0056u20.5319u63.2653u20.4472u20.6786u
ibs-5.6305a0.0.0.0.
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vgs950.5721m956.5095m956.5095m649.4836m942.0310m
vds1.5334265.5018m548.8877m1.77941.8938
vbs-548.8877m0.0.0.0.
vth819.0731m625.4655m625.4655m625.4619m615.2179m
vdsat143.5863m270.4055m270.4055m74.4708m268.7883m
vod131.4990m331.0440m331.0440m24.0217m326.8131m
beta2.0048m471.2720u1.4138m9.6929m465.7202u
gam eff678.0000m678.0000m678.0000m678.0000m678.0000m
gm230.8379u105.8696u345.4201u346.3295u115.7675u
gds625.7339n10.2678u1.7672u488.8814n120.9435n
gmb63.0612u35.4370u114.8098u122.2812u38.7179u
cdtot11.1126f10.9577f17.4995f70.1319f11.1053f
cgtot35.3704f35.6001f104.3176f512.9885f131.6175f
cstot33.9913f31.6197f83.7132f387.4480f103.5488f
cbtot30.3158f28.6968f63.1605f382.3310f71.5733f
cgs30.4785f30.5304f91.6915f371.2012f119.0351f
cgd2.0843f2.7726f4.9126f18.1321f1.8806f
subcktxi5.xmn21xi5.xmn18
element67:m068:m0
model67:nmos_3p3 68:nmos_3p3
regionSaturatiSaturati
id20.5510u20.5319u
ibs0.-5.8683a
ibd-5.8472a-3.3102a
vgs942.0310m869.6778m
vds942.0310m691.0077m
vbs0.-265.5018m
vth615.2179m735.0667m
vdsat268.7883m141.5769m
vod326.8131m134.6112m
beta465.7202u2.0007m
gam eff678.0000m678.0000m
gm115.2691u223.9965u
gds162.5101n850.8159n
gmb38.5591u67.6942u
cdtot13.5871f9.1769f
cgtot132.7380f36.2489f
cstot103.5626f35.4452f
cbtot72.9624f29.5635f
cgs119.0756f30.1084f
cgd2.9800f3.1008f
subcktxi5.xmp0
element79:m0
model79:pmos_3p3
regionSaturati
id-64.6983u
ibs0.
ibd34.7852p
vgs-1.0264
vds-2.1835
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vth-869.6275m
vdsat-151.4233m
vod-156.7586m
beta4.8766m
gam eff489.1245m
gm664.2119u
gds1.4768u
gmb173.0358u
cdtot107.3737f
cgtot520.8095f
cstot489.8453f
cbtot393.0871f
cgs467.4127f
cgd18.6927f
subcktxi5.xmp1xi5.xmp4xi5.xmp3xi5.xmp5xi5.xmp6
element80:m081:m082:m083:m084:m0
model80:pmos_3p3 81:pmos_3p3 82:pmos_3p3 83:pmos_3p3 84:pmos_3p3
regionSaturatiSaturatiSaturatiSaturatiSaturati
id-64.6982u-60.0377u-60.0377u-60.0377u-60.0377u
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ibd34.7862p6.4732a6.4732a4.9729p4.9083p
vgs-1.0264-1.2177-1.2177-1.0197-1.0197
vds-2.1835-386.4244m-386.4277m-1.9502-1.9488
vbs0.0.0.0.0.
vth-869.6275m-869.4656m-869.4656m-869.6291m-869.6291m
vdsat-151.4231m-291.5015m-291.5015m-146.8337m-146.8360m
vod-156.7584m-348.2825m-348.2825m-150.1168m-150.1201m
beta4.8766m1.1741m1.1741m4.8836m4.8836m
gam eff489.1245m489.1242m489.1242m489.1245m489.1245m
gm664.2112u302.9908u302.9912u635.7076u635.7029u
gds1.4768u12.4161u12.4158u1.4805u1.4810u
gmb173.0356u77.7560u77.7561u165.7678u165.7667u
cdtot107.3737f35.2689f35.2689f110.7724f110.7949f
cgtot520.8094f144.6231f144.6231f518.4552f518.4616f
cstot489.8452f147.0478f147.0478f487.4786f487.4798f
cbtot393.0870f117.9129f117.9128f395.9835f396.0011f
cgs467.4126f131.0624f131.0624f463.4270f463.4290f
cgd18.6927f8.9390f8.9389f19.3642f19.3691f
subcktxi5.xmp9xi5.xmp8xi5.xmp7xi5.xmp11xi5.xmp10
element85:m086:m087:m088:m089:m0
model85:pmos_3p3 86:pmos_3p3 87:pmos_3p3 88:pmos_3p3 89:pmos_3p3
regionSaturatiSaturatiSaturatiSaturatiSaturati
id-400.9343u-400.3901u-129.3968u-42.2597u-21.0057u
ibs0.0.0.0.0.
ibd1.9339p813.3504f17.7883a5.1936a4.4233a
vgs-1.2262-1.2262-1.2262-1.2189-1.2177
vds-1.8337-1.7674-807.3078m-1.2189-1.2177
vbs0.0.0.0.0.
vth-869.6299m-869.6304m-869.6371m-869.6342m-869.6342m
vdsat-296.7444m-296.7441m-296.7391m-291.3038m-290.4621m
vod-356.5954m-356.5950m-356.5882m-349.2507m-348.1139m
beta6.9996m6.9996m2.3332m778.9877u389.5909u
gam eff489.1245m489.1245m489.1245m489.1245m489.1245m
gm2.0213m2.0188m651.1398u217.4836u108.4466u
gds8.0608u8.3590u7.0420u1.3445u668.8953n
gmb514.5613u513.9819u166.1390u55.4804u27.6688u
cdtot148.6906f150.4441f78.8264f19.0739f15.3768f
cgtot845.5470f846.1993f286.6770f95.0578f47.5203f
cstot733.2445f733.2463f259.7120f98.2790f50.4359f
cbtot518.7239f519.8292f212.6538f75.8920f45.0909f
cgs785.6899f785.6951f261.9919f87.1401f43.5568f
cgd31.2710f31.9201f15.2070f4.6860f2.3430f
subcktxi5.xmp13xi5.xmp14xi5.xmp20xi5.xmp17xi5.xmp15
element90:m091:m092:m093:m094:m0
model90:pmos_3p3 91:pmos_3p3 92:pmos_3p3 93:pmos_3p3 94:pmos_3p3
regionSaturatiSaturatiSaturatiSaturatiSaturati
id-20.4475u-20.3794u-20.5510u-20.6788u-20.5319u
ibs0.0.0.0.0.
ibd877.0729a8.5305a13.3154p8.7666a3.0068p
vgs-1.1792-1.1792-1.1792-1.0263-1.1792
vds-1.5206-1.1792-2.3580-846.3077m-2.1648
vbs0.0.0.0.0.
vth-855.7277m-855.7277m-855.7277m-869.6368m-855.7277m
vdsat-270.1862m-270.1862m-270.1862m-151.3266m-270.1862m
vod-323.4637m-323.4637m-323.4637m-156.6191m-323.4637m
beta455.2863u455.2863u455.2863u1.6256m455.2863u
gam eff488.7257m488.7257m488.7257m489.1245m488.7257m
gm114.8017u114.3818u115.3887u213.6104u115.2856u
gds167.0837n239.5628n94.0945n962.3378n104.5123n
gmb29.6480u29.5460u29.7879u55.7258u29.7636u
cdtot31.8336f34.6847f27.9448f40.9206f28.6235f
cgtot346.6473f347.9475f345.5153f177.2794f345.6546f
cstot262.9433f262.9544f262.9339f167.6933f262.9351f
cbtot157.1473f158.7217f154.3683f136.9111f154.9108f
cgs327.1516f327.1839f327.1241f155.8254f327.1276f
cgd5.7781f7.0593f4.6638f9.8959f4.8007f
subcktxi5.xmp16xi5.xmp19xi5.xmp18
element95:m096:m097:m0
model95:pmos_3p3 96:pmos_3p3 97:pmos_3p3
regionSaturatiCutoffLinear
id-20.6788u-38.3755a23.1113f
ibs0.0.0.
ibd4.7380a6.815e-19-4.873e-27
vgs-1.2262229.4924p-3.3000
vds-379.9176m-2.6505229.4924p
vbs0.0.0.
vth-869.6401m-817.2634m-859.8494m
vdsat-296.7369m-36.5309m-1.5862
vod-356.5852m817.2634m-2.4402
beta388.8680u108.9148u54.9198u
gam eff489.1245m490.5206m490.6307m
gm101.7051u1.1106f5.4791f
gds4.7040u13.7206a100.7060u
gmb26.0602u294.0416a2.8319f
cdtot22.4039f1.8862f2.8286f
cgtot48.1857f918.8050a1.4835f
cstot51.7882f3.5802f3.5585f
cbtot52.6520f5.7077f5.2576f
cgs43.6699f212.6164a732.2662a
cgd3.0342f126.1381a735.1501a
自己顶一下，大家帮忙给看一下吧。包括了dummy管在内的原理图如下：
dummy管在图中由红色标注，我怀疑输入端的dummy管也有可能引起该问题，请大家帮忙出个主意，谢谢了。