Lecture 2 NMOS Technology 240-451 VLSI, 2000 Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut Lecture 2 NMOS Technology 240-451 VLSI, 2000

Design Abstraction Levels Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut Design Abstraction Levels 240-451 VLSI, 2000

Introduction to NMOS NMOS technology was divided into 3 layers : Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut Introduction to NMOS NMOS technology was divided into 3 layers : - Diffusion Layer - Poly Silicon - Metal 240-451 VLSI, 2000

Introduction to NMOS 240-451 VLSI, 2000 D G G S D S Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut Introduction to NMOS D S G G S D Poly cross with diffusion --> Field effect transistor (FET) 240-451 VLSI, 2000

The Basic Idea ... N-Channel - N-Switches are ON when the Gate is 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) 240-451 VLSI, 2000

Transistors as switches Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut Transistors as switches N Switch G S D 1 Passes “good zeros” P Switch G S D 1 Passes “good ones” 240-451 VLSI, 2000

โลหะไม่มีปฏิกริยากับเส้นอื่น Diffusion has C > Poly , Metal BUT!! 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. 240-451 VLSI, 2000

Department of Computer Engineering, Prince of Songkla University Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut MOS Transistor 240-451 VLSI, 2000

Current and transistor structure Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut Current and transistor structure G S D - + Vds Ids Vgd Vgs 240-451 VLSI, 2000

Current in transistor Ids = Q t S v E = Vds ; Vds low L t = L2 m Vds Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut Current in transistor Ids = Q t S v L mE E = Vds ; Vds low L t = L2 m Vds 240-451 VLSI, 2000

I flow and transistor will be ON Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut t a L2 Ids a Vgs Vgs > Vthreshold ; I flow and transistor will be ON 240-451 VLSI, 2000

The relation between current and voltage Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut The relation between current and voltage 240-451 VLSI, 2000

Capacitance Q = - Cg (Vgs - Vth) * C = eA D Q = -eWL (Vgs - Vth) D Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut Capacitance Q = - Cg (Vgs - Vth) * C = eA D Q = -eWL (Vgs - Vth) D 240-451 VLSI, 2000

Current in Transistor (Ids) Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut Current in Transistor (Ids) Ids = - meW (Vgs - Vth) Vds LD Vds = LD Ids meW (Vgs - Vth) R = L2 m Cg(Vgs - Vth) 240-451 VLSI, 2000

Current in Saturation Ids = meW (Vgs - Vth)2 2LD 240-451 VLSI, 2000 D Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut Current in Saturation Ids = meW (Vgs - Vth)2 2LD G S D 240-451 VLSI, 2000

Current in Nonsaturated Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut Current in Nonsaturated Ids = Cgm ((Vgs - Vth)Vds - Vds2 ) L2 2 240-451 VLSI, 2000

N Channel: on=closed when gate is high Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut Serial Parallel Structure (1) 1 G S D N Channel: on=closed when gate is high 240-451 VLSI, 2000

NMOS Transistors in serial/parallel connection 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 240-451 VLSI, 2000

P Channel: on=closed when gate is low Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut Serial Parallel Structure (2) P Channel: on=closed when gate is low G S D 240-451 VLSI, 2000

PMOS transistors serial/parallel connection Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut PMOS transistors serial/parallel connection 240-451 VLSI, 2000

“Inverter in the next slide” Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut Questions & Summary “Inverter in the next slide” 240-451 VLSI, 2000