020170
Full Member level 4
I want to know how to measure fully differential amp's spec,
I used LMH6550, National semiconductor macro spice model.
I thought I can know How to measure Fully differential opamp' spec if I compare simulation result with LMH6550 datasheet after simulating LMH6550 macro model.
In the LMH6550 datasheet, there is some spec like "small signal -3dB bandwidth", 400MHz
But I got the result only "344MHz" in Hspice simulation.
what do I wrong?
netlist and the result is following
**************************************************
Vdd Vdd gnd dc 5V
Vss Vss gnd dc -5V
X1 in- VCM Vdd out+ out- vss en in+ LMH6550
Rs VIn1 1 50
Rt 1 gnd 50
Rg1 1 in+ 365
Rf1 in+ out- 365
RL out- out+ 500
Rm gnd 2 25
Rg2 2 in- 365
Rf2 in- out+ 365
vin1 vin1 gnd ac 1
Ven en gnd dc 5
Vcm Vcm gnd dc 0
.op
.ac dec 10 10 11000G
*.dc vin1 -5 5 0.1
.print vm(out+) vm(out-)
*.tran 1n 10u
.end
I used LMH6550, National semiconductor macro spice model.
I thought I can know How to measure Fully differential opamp' spec if I compare simulation result with LMH6550 datasheet after simulating LMH6550 macro model.
In the LMH6550 datasheet, there is some spec like "small signal -3dB bandwidth", 400MHz
But I got the result only "344MHz" in Hspice simulation.
what do I wrong?
netlist and the result is following
**************************************************
Vdd Vdd gnd dc 5V
Vss Vss gnd dc -5V
X1 in- VCM Vdd out+ out- vss en in+ LMH6550
Rs VIn1 1 50
Rt 1 gnd 50
Rg1 1 in+ 365
Rf1 in+ out- 365
RL out- out+ 500
Rm gnd 2 25
Rg2 2 in- 365
Rf2 in- out+ 365
vin1 vin1 gnd ac 1
Ven en gnd dc 5
Vcm Vcm gnd dc 0
.op
.ac dec 10 10 11000G
*.dc vin1 -5 5 0.1
.print vm(out+) vm(out-)
*.tran 1n 10u
.end