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Hi all: I am a fresh man to design OPA, After I reading this two paper
1."Design Procedure for Two-Stage CMOS Operational Amplifiers Employing Current Buffer" Jirayuth Mahattanakul, IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS 2005, November, 2005
2."A Compensation Strategy for Two-Stage CMOS Opamps Based on Current Buffer" IEEE Trans. Circuits and Systs. I,vol.44, pp.257-262, Mar.1997,
I design a OPA in the file opa.pdf which can be found in the attachment, at the same, I design a bias circuit in the file opa_bias_improve.pdf which can be found in the attachment too, but afer I simulating the circuit use Hspice, I found the CurrentBuffer in the opa.pdf i.e. the transistor M6 is in the cutoff region, not in the saturation region. The netlist is in the file use_opa_bias_improve.sp.
At the same time, I found that the Vth of M6 is almost equal to the Vgs of M6, even larger than Vgs of M6, no matter what I change the w/l of the MB4 and MB6 which lie in the file opa_bias_improve.pdf.
After I use the other bias circuit in the file opa_bias.pdf which can be found in the attachment too, afer I simulating the circuit use Hspice, I found the CurrentBuffer in the opa.pdf i.e. the transistor M6 can be in the saturation region. The netlist is in the file use_opa_bias.sp
I do not know why, so I beg help. Help me please, thanx!!!!
1."Design Procedure for Two-Stage CMOS Operational Amplifiers Employing Current Buffer" Jirayuth Mahattanakul, IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS 2005, November, 2005
2."A Compensation Strategy for Two-Stage CMOS Opamps Based on Current Buffer" IEEE Trans. Circuits and Systs. I,vol.44, pp.257-262, Mar.1997,
I design a OPA in the file opa.pdf which can be found in the attachment, at the same, I design a bias circuit in the file opa_bias_improve.pdf which can be found in the attachment too, but afer I simulating the circuit use Hspice, I found the CurrentBuffer in the opa.pdf i.e. the transistor M6 is in the cutoff region, not in the saturation region. The netlist is in the file use_opa_bias_improve.sp.
At the same time, I found that the Vth of M6 is almost equal to the Vgs of M6, even larger than Vgs of M6, no matter what I change the w/l of the MB4 and MB6 which lie in the file opa_bias_improve.pdf.
After I use the other bias circuit in the file opa_bias.pdf which can be found in the attachment too, afer I simulating the circuit use Hspice, I found the CurrentBuffer in the opa.pdf i.e. the transistor M6 can be in the saturation region. The netlist is in the file use_opa_bias.sp
I do not know why, so I beg help. Help me please, thanx!!!!