A problem with an amp with cmfb

[zoe88]

Hello guys:
I have designed an amp with sc cmfb, yet when I sim the amp with cmfb , the gain has dropped dramatically. The amp is designed for an 80MHz-10bit-pipelined ADC., and the switching frequency is 80MHz. I don't know whether it' s the problem with the asymmetry between two output voltages. here is the netlist. Pls tell me anything that may help,thans a lot !I am beginner so pardon me if I have made any stupid mistake.

netlist for hspice(with SMIC 0.13um lib)

*lambdan kn33

.LIB 'D:\Program Files\HSPICE2010\smic-0.13\ms013_io33_v2p6.lib' tt

.subckt cmfb nop non ng11 ng12 ng13 ng21 ng22 ng23 ng31 ng32 ng33 ng41 ng42 ng43 ncm nb ncmfb

C11 n11 n1 0.1pf
C12 n1 n12 0.1pf
C21 nop ncmfb 0.2pf
C22 ncmfb non 0.2pf
C31 n21 n2 0.1pf
C32 n2 n22 0.1pf

M11 ncm ng11 n11 0 n33 w=0.02u l=0.13u
M12 nb ng12 n1 0 n33 w=0.02u l=0.13u
M13 ncm ng13 n12 0 n33 w=0.02u l=0.13u

M21 n11 ng21 nop 0 n33 w=0.02u l=0.13u
M22 ncmfb ng22 n1 0 n33 w=0.02u l=0.13u
M23 non ng23 n12 0 n33 w=0.02u l=0.13u

M31 nop ng31 n21 0 n33 w=0.02u l=0.13u
M32 ncmfb ng32 n2 0 n33 w=0.02u l=0.13u
M33 non ng33 n22 0 n33 w=0.02u l=0.13u

M41 ncm ng41 n21 0 n33 w=0.02u l=0.13u
M42 nb ng42 n2 0 n33 w=0.02u l=0.13u
M43 ncm ng43 n22 0 n33 w=0.02u l=0.13u
.ends

.subckt bcn nop non ninp ninn nvdd nb11 nb12 nb56 nb34 nb78 nb910
M11 n111 nb11 0 0 n33 w=35u l=1u
M12 n1211 nb12 n111 0 n33 w=30u l=1u
M1 n51 ninp n1211 0 n33 w=6u l=1u
M2 n62 ninn n1211 0 n33 w=6u l=1u
M5 n51 nb56 nvdd nvdd p33 w=14.85u l=1.20u
M6 n62 nb56 nvdd nvdd p33 w=14.85u l=1.20u
M3 nop nb34 n51 nvdd p33 w=17.00u l=0.18u
M4 non nb34 n62 nvdd p33 w=17.00u l=0.18u
M7 nop nb78 n79 0 n33 w=23.18u l=1.00u
M8 non nb78 n810 0 n33 w=23.18u l=1.00u
M9 n79 nb910 0 0 n33 w=11.51u l=2.00u
M10 n810 nb910 0 0 n33 w=11.51u l=2.00u
.ends

M11 n1112 nb11 0 0 n33 w=90u l=0.13u
M12 n112 nb12 n1112 0 n33 w=96u l=0.15u
M1 n51 ninp n112 0 n33 w=215.00u l=0.32u
M2 n62 ninn n112 0 n33 w=215.00u l=0.32u
M5 n51 nb56 nvdd nvdd p33 w=247.03u l=0.33u
M6 n62 nb56 nvdd nvdd p33 w=247.03u l=0.33u
M3 nop nb3 n51 nvdd p33 w=143.90u l=0.20u
M4 non nb4 n62 nvdd p33 w=143.90u l=0.20u
M7 nop nb7 n79 0 n33 w=66.80u l=0.13u
M8 non nb8 n810 0 n33 w=66.80u l=0.13u
M9 n79 nb910 0 0 n33 w=238.06u l=0.90u
M10 n810 nb910 0 0 n33 w=238.06u l=0.90u

.subckt bcp nop non ninp ninn nvdd nb11 nb12 nb56 nb34 nb78 nb910
M11 n111 nb11 nvdd nvdd p33 w=80u l=1u
M12 n1211 nb12 n111 nvdd p33 w=80u l=1u
M1 n91 ninp n1211 nvdd p33 w=40u l=1u
M2 n102 ninn n1211 nvdd p33 w=40u l=1u
M5 n53 nb56 nvdd nvdd p33 w=8.45u l=1.8u
M6 n64 nb56 nvdd nvdd p33 w=8.45u l=1.8u
M3 nop nb34 n53 nvdd p33 w=25.00u l=1.00u
M4 non nb34 n64 nvdd p33 w=25.00u l=1.00u
M7 nop nb78 n91 0 n33 w=18.27u l=0.70u
M8 non nb78 n102 0 n33 w=18.27u l=0.70u
M9 n91 nb910 0 0 n33 w=10.54u l=1.00u
M10 n102 nb910 0 0 n33 w=10.54u l=1.00u
.ends

VDD nvdd 0 3.3

Vb12 nb12 0 1.50
Vb11 nb11 0 1.00
Vb56 nb56 0 2
$Vb910 nb910 0 0.99

Vb11n nb11n 0 1.1
Vb12n nb12n 0 1.3
Vb56n nb56n 0 1.3
Vb34n nb34n 0 1.2
Vb78n nb78n 0 1.5
Vb910n nb910n 0 1.1

Vb11p nb11p 0 2.2
Vb12p nb12p 0 1.7
Vb56p nb56p 0 1.5
Vb34p nb34p 0 1.1
Vb78p nb78p 0 1.2
Vb910p nb910p 0 1.2

Cl1 nop 0 4.0pF
Cl2 non 0 4.0pF

xbcn nb3 nb4 n51 n62 nvdd nb11n nb12n nb56n nb34n nb78n nb910n bcn
xbcp nb7 nb8 n79 n810 nvdd nb11p nb12p nb56p nb34p nb78p nb910p bcp
xcmfb nop non ng11 ng12 ng13 ng21 ng22 ng23 ng31 ng32 ng33 ng41 ng42 ng43 ncm nb nb910 cmfb

v11 ng11 0 PULSE 3.3 0 -0.05n 0.125n 0.125n 6.225n 12.5n
v12 ng12 0 PULSE 3.3 0 -0.05n 0.125n 0.125n 6.225n 12.5n
v13 ng13 0 PULSE 3.3 0 -0.05n 0.125n 0.125n 6.225n 12.5n

v21 ng21 0 PULSE 0 3.3 0.00n 0.125n 0.125n 6.050n 12.5n
v22 ng22 0 PULSE 0 3.3 0.00n 0.125n 0.125n 6.125n 12.5n
v23 ng23 0 PULSE 0 3.3 0.00n 0.125n 0.125n 6.050n 12.5n

v31 ng31 0 PULSE 3.3 0 -0.05n 0.125n 0.125n 6.225n 12.5n
v32 ng32 0 PULSE 3.3 0 -0.05n 0.125n 0.125n 6.225n 12.5n
v33 ng33 0 PULSE 3.3 0 -0.05n 0.125n 0.125n 6.225n 12.5n

v41 ng41 0 PULSE 0 3.3 0.00n 0.125n 0.125n 6.050n 12.5n
v42 ng42 0 PULSE 0 3.3 0.00n 0.125n 0.125n 6.125n 12.5n
v43 ng43 0 PULSE 0 3.3 0.00n 0.125n 0.125n 6.050n 12.5n

Vcm ncm 0 1.6

Vbias nb 0 0.99

Vinp ninp 0 sin(1.6 0.000005 5k)
Vinn ninn 0 sin(1.6 -0.000005 5k)

.tran 1us 0.8ms

.print I(M1) I(M5) I(M9)

.option captab
.end

- - - Updated - - -

The amp is a classic folded cascode with gain boosted technology, and the aux amp is also a folded cascode. Thank you again!

 

[zoe88]

we can see that with cmfb the curve is much smaller and the thing that's ealy weired is that the curve changes from sin curve to stages...:-?