Lecture 2

1. Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut Lecture 2 NMOS Technology

2. Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut Design Abstraction Levels

3. - Diffusion Layer - Poly Silicon - Metal Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut Introduction to NMOS NMOS technology was divided into 3 layers :

4. D G S Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut Introduction to NMOS G S D Poly cross with diffusion --> Field effect transistor (FET)

5. Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut The Basic Idea ... • N-Channel - N-Switches are ON when the Gate is • HIGH and OFF when the Gate is LOW • P-Channel - P-Switches are OFF when the Gate is • HIGH and ON when the Gate is LOW • (ON == Circuit between Source and Drain)

6. D G D S G S Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut Transistors as switches N Switch 0 1 Passes “good zeros” P Switch 0 Passes “good ones” 1

7. Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut General Properties • โลหะไม่มีปฏิกริยากับเส้นอื่น • Diffusion has C> Poly , Metal BUT!! • Poly and metal have R > Diffusion.

8. Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut MOS Transistor

9. Ids D - Vgd G S + Vds + + Vgs Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut Current and transistor structure

10. Ids = Q t L mE S v E = Vds ; Vds low L t = L2 mVds Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut Current in transistor

11. Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut t a L2 Idsa Vgs Vgs > Vthreshold ; I flow and transistor will be ON

12. Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut The relation between current and voltage

13. Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut Capacitance Q = - Cg (Vgs - Vth) * C = eA D Q = -eWL (Vgs - Vth) D

14. Ids = - meW (Vgs - Vth) Vds LD Vds = LD Ids meW (Vgs - Vth) R = L2 mCg(Vgs - Vth) Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut Current in Transistor (Ids)

15. D G S Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut Current in Saturation Ids=meW (Vgs - Vth)2 2LD

16. Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut Current in Nonsaturated Ids= Cgm ((Vgs - Vth)Vds - Vds2 ) L2 2

17. D 1 G D S D 1 1 G G D S S 1 G S Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut Serial Parallel Structure (1) N Channel: on=closed when gate is high

18. Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut NMOS Transistors in serial/parallel connection • Transistors can be thought as a switch controlled by its gate signal • NMOS switch closes when switch control input is high

19. D 0 G D S D 0 0 G G D S S 0 G S P Channel: on=closed when gate is low Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut Serial Parallel Structure (2)

20. Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut PMOS transistors serial/parallel connection

21. Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut Questions & Summary “Inverter in the next slide”