MOS Inverters: Basic Properties and Properties in CMOS Inverters

1. Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut Lecture 3 MOS INVERTERS

2. Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut Basic Properties

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

4. 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

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

6. 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 Vgs(enh) = Vin

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

8. Slope = Vout Vin Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut Relation between Vout & Vin

9. A Vout Vin Ids = meW (Vgs - Vth)2 2 LD Ids = meWpu (- Vthd)2 ; Vgs = 0 2 DLpu Ids = meWpd (Vinv - Vthe)2 ; Vgs = Vinv 2 DLpd Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut Zpu / Zpd in nMOS Inverter * Steady state depletion enhance

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

11. Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut Zpu / Zpd in nMOS Inverter Vinv = Vthe - Vthd (Zpu /Zpd )1/2 Vt = 0.2 VDD Vtd = -0.6 VDD Vinv = 0.5 VDD Zpu/Zpd = 4 /1

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

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

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

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

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

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

18. Wp = 2.5 Wn Lp Ln Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut CMOS Inverter transistor See the example in your book

19. 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

20. 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 )

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