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Folded Cascode Op-amp
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Given Values:
Bias voltages: Power Budget=1mW Cu1)V1=1!"#V Vdd=$!#V
B1=#%u&
')V'=%V Vss=-$!#V
B'=#%u&$)V$=-1!"#V BW=1(*
B$='#u&
Vswing=#VB+='#u&
=
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Calculation:Von calculation:
Von,pmos)=Vsg-Vtp ,Vtp=-%!)
Von,nmos)=Vgs-Vtn ,Vtn= %!")
Von,.%)=Vsg-/Vtp/=$!#-1!"#-%!=%!0#V
Von,.0)=Vgs- Vtn =-1!"#$!#-%!"=1!%#V
&s we 2ave decided t2e output swing as #V3soVdd-Vss=sum,Von)$3#3"30Vswing3so
4um,Von)$3"3#='-Von0='-1!%#=%!0#V
We are dividing %!0#V among .$3.#3."3as 5ollowing,rea
Von#=%!'#V3Von"=%!'#V3so Von$=%!0#-',%!'#)=%!+#V
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Calculation,cont!)W78 calculation :
&s we (now t2e values o5 Von and 9d 5or t2e mos5ets3 so u
5ollowing e;uation3 we can get t2is ratio6
W78='9d7,(n!0#> as Von=%!'#V39d='#u&
,W78)#3>=1!0" as Von=%!'#V39d='#u&
,W78)1131'31$31+=%!0>$# as Von=%!0#V39d=#%u&
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Calculation,cont!)
Calculation o5 ,W78)1 using gain e;uation:Gain,di?)=gm17gout=@ gm1=Gain,di?) A gout
W2ere3
gout=,gds$!gds"7gm"),gds#,gds1gds0)7gm#)
,1)ere3gds=lamda9d3so
gds$=lamda3p9d=%!''#u=#u4 ,lamda3p%!
lamda3n=%!$)
4imilarl3
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Calculation,cont!)
gm"=,'9d(p
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E2eoretical vs simulation result
Parameters Theoretical values Practical(simu
values
Gain >>dB ">!10dB
P4 ->!0+dB -%!>$dB
Power dissipation 1%#%uW 1>>!0"uW
Gain BW product #%%.* 0!">.*
4wing #V +!10V
V13'3$ 1!"#3%3-1!"#V 1!0>003'#>mV3-
4lew ate '# V7us %!0'V7us
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Fre;uenc esponse,simulation
Plot wit2 dB:
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Fre;uenc esponse,cont):
% dB BW:
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Fre;uenc esponse,cont):
-$ dB BW:
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Fre;uenc esponse,cont):
4wing:
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Fre;uenc esponse,cont):
4lew ate:
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Fre;uenc esponse,cont):
Common .ode Gain
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8aout o5 t2e 5olded cascode opamp:
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8aout ules:
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E&D HOI