Department of Computer Engineering Prince of Songkla University

Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut Lecture 3 MOS INVERTERS 240 -451 VLSI, 1

Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut Basic Properties 240 -451 VLSI, 2

Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut Basic Properties Require Large “R” for limitation in current 240 -451 VLSI, 3

Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut Basic Properties • Vin > Vth transistor ON Vout = “ 0” pull down • Vin < Vth transistor OFF Vout = “ 1” pull up 240 -451 VLSI, 4

Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut NMOS Transistor (Depletion & Enhance( NMOS Depletion V = 0 but still has Ids 240 -451 VLSI, 5

Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut Inverter transistor VDD = Vds(dep) + Vds(enh( Vds(enh) = VDD - Vds(dep( Vout = Vds(enh ( Ids(dep) = Ids(enh( Vgs(dep) = 0 240 -451 VLSI, Vgs(enh) = Vin 6

Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut Inverter transistor n. MOS (depletion) => pull-up n. MOS (enhance) => pull-down 240 -451 VLSI, 7

Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut Relation between Vout & Vin Slope = Vout Vin 240 -451 VLSI, 8

Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut Zpu / Zpd in n. MOS Inverter A Vin Vout *Steady state Ids = me. W (Vgs - Vth)2 2 LD depletion Ids = me. Wpu (- Vthd)2 ; Vgs = 0 2 DLpu enhance Ids = me. Wpd (Vinv - Vthe)2 ; Vgs = Vinv DLpd 240 -451 VLSI, 2 9

Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut Zpu / Zpd in n. MOS Inverter Ids (depletion) = Ids (enhance) Wpd (Vinv - Vthe)2 = Wpu (- Vthd)2 Lpd Lpu Let Zpd = Lpd ; Zpu = Lpu Wpd Wpu ) 1 Vinv - Vthe)2 = Zpd 240 -451 VLSI, 1 (- Vthd)2 Zpu 10

Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut Zpu / Zpd in n. MOS Inverter Vinv = Vthe ) Vthd Zpu / Zpd )1/2 Vt = 0. 2 VDD Vtd = -0. 6 VDD Vinv = 0. 5 VDD Zpu/ Zpd = 4 /1 240 -451 VLSI, 11

Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut Use R to pull-up 240 -451 VLSI, 12

Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut Use n. MOS(depletion) to pull-up • Lose power while Vin=1 240 -451 VLSI, 13

Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut Use n. MOS to pull-up Lose power when VGG = VDD 240 -451 VLSI, 14

Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut Use p. MOS to pull-up I =0 npmos < nnmos 240 -451 VLSI, 15

Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut CMOS Inverter transistor Ids = me. W (Vgs - Vth)2 2 LD K = me 2 D b = KW L Ids = b (Vgs - Vth)2 2 240 -451 VLSI, 16

Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut CMOS Inverter transistor Steady state b = KWn Ln b = KWp Lp Idsp = - Idsn = bp(Vin - VDD - Vthp)2 2 Idsn = bn(Vin - Vthn)2 2 240 -451 VLSI, 17

Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut CMOS Inverter transistor Wp = 2. 5 Wn Lp Ln See the example in your book 240 -451 VLSI, 18

Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut How to calculate delay K = Zpu/ Zpd Down delay = f t Up delay = f K t See the example in your book 240 -451 VLSI, 19

Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut How to calculate R & C VLSI technology defined diffusion and poly layer = 2 l * (2521 ; l = 3 mm ) 240 -451 VLSI, 20

Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut How to calculate R & C R = r. L A A = tw If L=W= 1 then R = 240 -451 VLSI, r t R = r. L tw See the example in your book 21