Jan 14, 2010 #1 R rage_speed Newbie level 6 Joined Sep 1, 2008 Messages 12 Helped 2 Reputation 4 Reaction score 2 Trophy points 1,283 Activity points 1,394 Hi, I was designing a CMOS common source amplifier using tsmc018(level = 49) model MOS. I was trying to increase the DC gain by reducing the overdrive of M1 and correspondingly increasing its W/L of M1 keeping the current constant at 20u. W/L of M2 was constant throughout. But the gain became constant (~68.8) below 140mV Overdrive. Can somebody explain why the gain saturated? I have attached the schematic. Thanks in advance
Hi, I was designing a CMOS common source amplifier using tsmc018(level = 49) model MOS. I was trying to increase the DC gain by reducing the overdrive of M1 and correspondingly increasing its W/L of M1 keeping the current constant at 20u. W/L of M2 was constant throughout. But the gain became constant (~68.8) below 140mV Overdrive. Can somebody explain why the gain saturated? I have attached the schematic. Thanks in advance
Jan 14, 2010 #2 R rage_speed Newbie level 6 Joined Sep 1, 2008 Messages 12 Helped 2 Reputation 4 Reaction score 2 Trophy points 1,283 Activity points 1,394 The Schematic of the common source Amp. And the MOS model * T58F SPICE BSIM3 VERSION 3.1 PARAMETERS * * SPICE 3f5 Level 8, Star-HSPICE Level 49, UTMOST Level 8 * * DATE: Oct 31/05 * LOT: T58F WAF: 9005 * Temperature_parameters=Default .MODEL CMOSN NMOS ( LEVEL = 49 +VERSION = 3.1 TNOM = 27 TOX = 4.1E-9 +XJ = 1E-7 NCH = 2.3549E17 VTH0 = 0.3662473 +K1 = 0.5864999 K2 = 1.127266E-3 K3 = 1E-3 +K3B = 0.0294061 W0 = 1E-7 NLX = 1.630684E-7 +DVT0W = 0 DVT1W = 0 DVT2W = 0 +DVT0 = 1.2064649 DVT1 = 0.4215486 DVT2 = 0.0197749 +U0 = 273.8094484 UA = -1.40499E-9 UB = 2.408323E-18 +UC = 6.504826E-11 VSAT = 1.355009E5 A0 = 2 +AGS = 0.4449958 B0 = 1.901075E-7 B1 = 4.99995E-6 +KETA = -0.0164863 A1 = 3.868769E-4 A2 = 0.4640272 +RDSW = 123.3376355 PRWG = 0.5 PRWB = -0.197728 +WR = 1 WINT = 0 LINT = 1.690044E-8 +XL = 0 XW = -1E-8 DWG = -4.728719E-9 +DWB = -2.452411E-9 VOFF = -0.0948017 NFACTOR = 2.1860065 +CIT = 0 CDSC = 2.4E-4 CDSCD = 0 +CDSCB = 0 ETA0 = 2.230928E-3 ETAB = 6.028975E-5 +DSUB = 0.0145467 PCLM = 1.3822069 PDIBLC1 = 0.1762787 +PDIBLC2 = 1.66653E-3 PDIBLCB = -0.1 DROUT = 0.7694691 +PSCBE1 = 8.91287E9 PSCBE2 = 7.349607E-9 PVAG = 1.685917E-3 +DELTA = 0.01 RSH = 6.7 MOBMOD = 1 +PRT = 0 UTE = -1.5 KT1 = -0.11 +KT1L = 0 KT2 = 0.022 UA1 = 4.31E-9 +UB1 = -7.61E-18 UC1 = -5.6E-11 AT = 3.3E4 +WL = 0 WLN = 1 WW = 0 +WWN = 1 WWL = 0 LL = 0 +LLN = 1 LW = 0 LWN = 1 +LWL = 0 CAPMOD = 2 XPART = 0.5 +CGDO = 8.23E-10 CGSO = 8.23E-10 CGBO = 1E-12 +CJ = 9.466429E-4 PB = 0.8 MJ = 0.3820266 +CJSW = 2.608154E-10 PBSW = 0.8 MJSW = 0.102322 +CJSWG = 3.3E-10 PBSWG = 0.8 MJSWG = 0.102322 +CF = 0 PVTH0 = -2.199373E-3 PRDSW = -0.9368961 +PK2 = 1.593254E-3 WKETA = -2.880976E-3 LKETA = 7.165078E-3 +PU0 = 6.777519 PUA = 5.505418E-12 PUB = 8.84133E-25 +PVSAT = 2.006286E3 PETA0 = 1.003159E-4 PKETA = -6.759277E-3 +NOIMOD=2.0E+00 NOIA=1.3182567385564E+19 +NOIB=144543.977074592 NOIC=-1.24515784572817E-12 EF=0.92 EM=41000000 ) * * * flicker noise parameters above added manually from some other process * .MODEL CMOSP PMOS ( LEVEL = 49 +VERSION = 3.1 TNOM = 27 TOX = 4.1E-9 +XJ = 1E-7 NCH = 4.1589E17 VTH0 = -0.3906012 +K1 = 0.5341312 K2 = 0.0395326 K3 = 0 +K3B = 7.4916211 W0 = 1E-6 NLX = 1.194072E-7 +DVT0W = 0 DVT1W = 0 DVT2W = 0 +DVT0 = 0.5060555 DVT1 = 0.2423835 DVT2 = 0.1 +U0 = 115.6894042 UA = 1.573746E-9 UB = 1.874308E-21 +UC = -1E-10 VSAT = 1.130982E5 A0 = 1.9976555 +AGS = 0.4186945 B0 = 1.949178E-7 B1 = 6.422908E-7 +KETA = 0.0166345 A1 = 0.4749146 A2 = 0.300003 +RDSW = 198.321294 PRWG = 0.5 PRWB = -0.4986647 +WR = 1 WINT = 0 LINT = 2.94454E-8 +XL = 0 XW = -1E-8 DWG = -2.798724E-8 +DWB = -4.83797E-10 VOFF = -0.095236 NFACTOR = 2 +CIT = 0 CDSC = 2.4E-4 CDSCD = 0 +CDSCB = 0 ETA0 = 1.035504E-3 ETAB = -4.358398E-4 +DSUB = 1.816555E-3 PCLM = 1.3299898 PDIBLC1 = 1.766563E-3 +PDIBLC2 = 7.728395E-7 PDIBLCB = -1E-3 DROUT = 1.011891E-3 +PSCBE1 = 4.872184E10 PSCBE2 = 5E-10 PVAG = 0.0209921 +DELTA = 0.01 RSH = 7.7 MOBMOD = 1 +PRT = 0 UTE = -1.5 KT1 = -0.11 +KT1L = 0 KT2 = 0.022 UA1 = 4.31E-9 +UB1 = -7.61E-18 UC1 = -5.6E-11 AT = 3.3E4 +WL = 0 WLN = 1 WW = 0 +WWN = 1 WWL = 0 LL = 0 +LLN = 1 LW = 0 LWN = 1 +LWL = 0 CAPMOD = 2 XPART = 0.5 +CGDO = 6.35E-10 CGSO = 6.35E-10 CGBO = 1E-12 +CJ = 1.144521E-3 PB = 0.8468686 MJ = 0.4099522 +CJSW = 2.490749E-10 PBSW = 0.8769118 MJSW = 0.3478565 +CJSWG = 4.22E-10 PBSWG = 0.8769118 MJSWG = 0.3478565 +CF = 0 PVTH0 = 2.302018E-3 PRDSW = 9.0575312 +PK2 = 1.821914E-3 WKETA = 0.0222457 LKETA = -1.495872E-3 +PU0 = -1.5580645 PUA = -6.36889E-11 PUB = 1E-21 +PVSAT = 49.8420442 PETA0 = 2.827793E-5 PKETA = -2.536564E-3 + NOIMOD=2.0E+00 NOIA=3.57456993317604E+18 NOIB=2500 + NOIC=2.61260020285845E-11 EF=1.1388 EM=41000000 ) * * * flicker noise parameters above added manually from some other process *
The Schematic of the common source Amp. And the MOS model * T58F SPICE BSIM3 VERSION 3.1 PARAMETERS * * SPICE 3f5 Level 8, Star-HSPICE Level 49, UTMOST Level 8 * * DATE: Oct 31/05 * LOT: T58F WAF: 9005 * Temperature_parameters=Default .MODEL CMOSN NMOS ( LEVEL = 49 +VERSION = 3.1 TNOM = 27 TOX = 4.1E-9 +XJ = 1E-7 NCH = 2.3549E17 VTH0 = 0.3662473 +K1 = 0.5864999 K2 = 1.127266E-3 K3 = 1E-3 +K3B = 0.0294061 W0 = 1E-7 NLX = 1.630684E-7 +DVT0W = 0 DVT1W = 0 DVT2W = 0 +DVT0 = 1.2064649 DVT1 = 0.4215486 DVT2 = 0.0197749 +U0 = 273.8094484 UA = -1.40499E-9 UB = 2.408323E-18 +UC = 6.504826E-11 VSAT = 1.355009E5 A0 = 2 +AGS = 0.4449958 B0 = 1.901075E-7 B1 = 4.99995E-6 +KETA = -0.0164863 A1 = 3.868769E-4 A2 = 0.4640272 +RDSW = 123.3376355 PRWG = 0.5 PRWB = -0.197728 +WR = 1 WINT = 0 LINT = 1.690044E-8 +XL = 0 XW = -1E-8 DWG = -4.728719E-9 +DWB = -2.452411E-9 VOFF = -0.0948017 NFACTOR = 2.1860065 +CIT = 0 CDSC = 2.4E-4 CDSCD = 0 +CDSCB = 0 ETA0 = 2.230928E-3 ETAB = 6.028975E-5 +DSUB = 0.0145467 PCLM = 1.3822069 PDIBLC1 = 0.1762787 +PDIBLC2 = 1.66653E-3 PDIBLCB = -0.1 DROUT = 0.7694691 +PSCBE1 = 8.91287E9 PSCBE2 = 7.349607E-9 PVAG = 1.685917E-3 +DELTA = 0.01 RSH = 6.7 MOBMOD = 1 +PRT = 0 UTE = -1.5 KT1 = -0.11 +KT1L = 0 KT2 = 0.022 UA1 = 4.31E-9 +UB1 = -7.61E-18 UC1 = -5.6E-11 AT = 3.3E4 +WL = 0 WLN = 1 WW = 0 +WWN = 1 WWL = 0 LL = 0 +LLN = 1 LW = 0 LWN = 1 +LWL = 0 CAPMOD = 2 XPART = 0.5 +CGDO = 8.23E-10 CGSO = 8.23E-10 CGBO = 1E-12 +CJ = 9.466429E-4 PB = 0.8 MJ = 0.3820266 +CJSW = 2.608154E-10 PBSW = 0.8 MJSW = 0.102322 +CJSWG = 3.3E-10 PBSWG = 0.8 MJSWG = 0.102322 +CF = 0 PVTH0 = -2.199373E-3 PRDSW = -0.9368961 +PK2 = 1.593254E-3 WKETA = -2.880976E-3 LKETA = 7.165078E-3 +PU0 = 6.777519 PUA = 5.505418E-12 PUB = 8.84133E-25 +PVSAT = 2.006286E3 PETA0 = 1.003159E-4 PKETA = -6.759277E-3 +NOIMOD=2.0E+00 NOIA=1.3182567385564E+19 +NOIB=144543.977074592 NOIC=-1.24515784572817E-12 EF=0.92 EM=41000000 ) * * * flicker noise parameters above added manually from some other process * .MODEL CMOSP PMOS ( LEVEL = 49 +VERSION = 3.1 TNOM = 27 TOX = 4.1E-9 +XJ = 1E-7 NCH = 4.1589E17 VTH0 = -0.3906012 +K1 = 0.5341312 K2 = 0.0395326 K3 = 0 +K3B = 7.4916211 W0 = 1E-6 NLX = 1.194072E-7 +DVT0W = 0 DVT1W = 0 DVT2W = 0 +DVT0 = 0.5060555 DVT1 = 0.2423835 DVT2 = 0.1 +U0 = 115.6894042 UA = 1.573746E-9 UB = 1.874308E-21 +UC = -1E-10 VSAT = 1.130982E5 A0 = 1.9976555 +AGS = 0.4186945 B0 = 1.949178E-7 B1 = 6.422908E-7 +KETA = 0.0166345 A1 = 0.4749146 A2 = 0.300003 +RDSW = 198.321294 PRWG = 0.5 PRWB = -0.4986647 +WR = 1 WINT = 0 LINT = 2.94454E-8 +XL = 0 XW = -1E-8 DWG = -2.798724E-8 +DWB = -4.83797E-10 VOFF = -0.095236 NFACTOR = 2 +CIT = 0 CDSC = 2.4E-4 CDSCD = 0 +CDSCB = 0 ETA0 = 1.035504E-3 ETAB = -4.358398E-4 +DSUB = 1.816555E-3 PCLM = 1.3299898 PDIBLC1 = 1.766563E-3 +PDIBLC2 = 7.728395E-7 PDIBLCB = -1E-3 DROUT = 1.011891E-3 +PSCBE1 = 4.872184E10 PSCBE2 = 5E-10 PVAG = 0.0209921 +DELTA = 0.01 RSH = 7.7 MOBMOD = 1 +PRT = 0 UTE = -1.5 KT1 = -0.11 +KT1L = 0 KT2 = 0.022 UA1 = 4.31E-9 +UB1 = -7.61E-18 UC1 = -5.6E-11 AT = 3.3E4 +WL = 0 WLN = 1 WW = 0 +WWN = 1 WWL = 0 LL = 0 +LLN = 1 LW = 0 LWN = 1 +LWL = 0 CAPMOD = 2 XPART = 0.5 +CGDO = 6.35E-10 CGSO = 6.35E-10 CGBO = 1E-12 +CJ = 1.144521E-3 PB = 0.8468686 MJ = 0.4099522 +CJSW = 2.490749E-10 PBSW = 0.8769118 MJSW = 0.3478565 +CJSWG = 4.22E-10 PBSWG = 0.8769118 MJSWG = 0.3478565 +CF = 0 PVTH0 = 2.302018E-3 PRDSW = 9.0575312 +PK2 = 1.821914E-3 WKETA = 0.0222457 LKETA = -1.495872E-3 +PU0 = -1.5580645 PUA = -6.36889E-11 PUB = 1E-21 +PVSAT = 49.8420442 PETA0 = 2.827793E-5 PKETA = -2.536564E-3 + NOIMOD=2.0E+00 NOIA=3.57456993317604E+18 NOIB=2500 + NOIC=2.61260020285845E-11 EF=1.1388 EM=41000000 ) * * * flicker noise parameters above added manually from some other process *
Jan 14, 2010 #3 D dick_freebird Advanced Member level 7 Joined Mar 4, 2008 Messages 8,973 Helped 2,333 Reputation 4,683 Reaction score 2,515 Trophy points 1,393 Location USA Activity points 71,490 Single stage gain is gm*rout. gm has a peak, beyond which you can do no better for that. Rout is the parallel combination of load and active drain impedances, perhaps the load sets a ceiling there. Maybe if you decompose the problem into these elements it will become more clear, and show you where the improvement might come easiest.
Single stage gain is gm*rout. gm has a peak, beyond which you can do no better for that. Rout is the parallel combination of load and active drain impedances, perhaps the load sets a ceiling there. Maybe if you decompose the problem into these elements it will become more clear, and show you where the improvement might come easiest.
Jan 15, 2010 #4 R rage_speed Newbie level 6 Joined Sep 1, 2008 Messages 12 Helped 2 Reputation 4 Reaction score 2 Trophy points 1,283 Activity points 1,394 dick_freebird said: Single stage gain is gm*rout. gm has a peak, beyond which you can do no better for that. Rout is the parallel combination of load and active drain impedances, perhaps the load sets a ceiling there. Maybe if you decompose the problem into these elements it will become more clear, and show you where the improvement might come easiest. Click to expand... Thanks for replying. I am keeping the current constant so that Rout remains constant there by the output pole remains constant. And to see the maximum gain I can get with that Rout I am trying to increase the gm by changing Vov and W/L of M1. Is there a way to plot the gm for a constant current because we need to change both Vov & W/L. Thanks
dick_freebird said: Single stage gain is gm*rout. gm has a peak, beyond which you can do no better for that. Rout is the parallel combination of load and active drain impedances, perhaps the load sets a ceiling there. Maybe if you decompose the problem into these elements it will become more clear, and show you where the improvement might come easiest. Click to expand... Thanks for replying. I am keeping the current constant so that Rout remains constant there by the output pole remains constant. And to see the maximum gain I can get with that Rout I am trying to increase the gm by changing Vov and W/L of M1. Is there a way to plot the gm for a constant current because we need to change both Vov & W/L. Thanks
Jan 15, 2010 #5 B Braski Full Member level 3 Joined Dec 22, 2009 Messages 154 Helped 32 Reputation 64 Reaction score 28 Trophy points 1,308 Location Florence (ITALY) Activity points 2,384 This is the same topic posted in IC section...the reason holds...weak inversion->exp equations->gain saturation to ID/nVt with n slope factor.
This is the same topic posted in IC section...the reason holds...weak inversion->exp equations->gain saturation to ID/nVt with n slope factor.
Jan 15, 2010 #6 R rage_speed Newbie level 6 Joined Sep 1, 2008 Messages 12 Helped 2 Reputation 4 Reaction score 2 Trophy points 1,283 Activity points 1,394 @ Braski Can you please elaborate or direct me to some material on the topic. Thanks