Jun 23, 2006 #1 W wael_wael Full Member level 4 Joined Dec 3, 2005 Messages 221 Helped 5 Reputation 10 Reaction score 2 Trophy points 1,298 Activity points 2,760 Hi friends coulde you help me to find VB1, VB2 in the folded cascode OP AMP regards
Jun 23, 2006 #2 L lavitaebelle Member level 4 Joined Jan 26, 2006 Messages 73 Helped 24 Reputation 48 Reaction score 12 Trophy points 1,288 Activity points 2,131 To maximize the output swing, Vb1=vdd-(Veff4+Vt5+Veff5)----(=vdd-vt-2Veff, neglecting body effect and same veff) Vb2=Veff10+Vt8+Veff8----(=Vt+2veff) Here veff=Vgs-Vt The output can swing 2 veff above ground and below Vdd.
To maximize the output swing, Vb1=vdd-(Veff4+Vt5+Veff5)----(=vdd-vt-2Veff, neglecting body effect and same veff) Vb2=Veff10+Vt8+Veff8----(=Vt+2veff) Here veff=Vgs-Vt The output can swing 2 veff above ground and below Vdd.
Jun 24, 2006 #3 W wael_wael Full Member level 4 Joined Dec 3, 2005 Messages 221 Helped 5 Reputation 10 Reaction score 2 Trophy points 1,298 Activity points 2,760 thanx in the same circuit how i can calculate the (W/L)6, (W/L)8 regards Added after 27 minutes: hi friends actualy i am looking to desin this circuit (LINK) https://img98.imageshack.us/my.php?image=tmp86398eb.jpg i have problem how i can find the sizes of mos. thanks
thanx in the same circuit how i can calculate the (W/L)6, (W/L)8 regards Added after 27 minutes: hi friends actualy i am looking to desin this circuit (LINK) https://img98.imageshack.us/my.php?image=tmp86398eb.jpg i have problem how i can find the sizes of mos. thanks
Jun 25, 2006 #4 L lavitaebelle Member level 4 Joined Jan 26, 2006 Messages 73 Helped 24 Reputation 48 Reaction score 12 Trophy points 1,288 Activity points 2,131 The two things that determine the W/L are the bias current and Overdrive voltage(Vgs-Vt). You need to fix the overdrive voltage. Usually 100-200mV is a good number. W/L=2Id/(uo*Cox*Vov²) for a long channel device.
The two things that determine the W/L are the bias current and Overdrive voltage(Vgs-Vt). You need to fix the overdrive voltage. Usually 100-200mV is a good number. W/L=2Id/(uo*Cox*Vov²) for a long channel device.
Jun 26, 2006 #5 W wael_wael Full Member level 4 Joined Dec 3, 2005 Messages 221 Helped 5 Reputation 10 Reaction score 2 Trophy points 1,298 Activity points 2,760 i got it thanx