Question

4 x 106-__ Vds (cm/s) 0 1.25 as (V)- Figure P11.13 I Figure for Problems l 1·13 and 1 1 . 14. Problems 11.14 Consider an NMOS transistor with a threshold voltage of VTN-0.4 V. Plot, on the same graph, Vps(sat) over the range 0s VGs 3 V for (a) an ideal MOSFET (constant mobility) and (b) a device whose drift velocity is given in Figure P11.13.

Answer 1

11.14 (a) For Ves VN the NMOS transistor operates in cut-off region and the drain-to-source voltage will be zero. Thus, VDs 0 V for Ves 0.4 V And VGs>0.4 V and Vpsza VGs -VN = Ves-0.4 _ Tabulate the values as shown below VGs (Volts) a (Volts) 0 0 0.4 0 0.8 0.4 1.2 0.8 1.2 1.6 1.6 2.2 1.8 2.4 2 2.2 2.6 2.8 2.4 3.0 2.6

Plot DS(sar over the range 0<Ves 3 as shown below. 3 2.5 2 1.5 0.5 1.5 2 0.5 2.5 3 V GS (volts) (b) Consider the drift velocity shown below 4 x 106 Vds (cm/s) 1.25 VDs (V) For Vns 21.25 V, the drift velocity remains constant. Thus, the drift DS velocity remains at 1.25 V after reaching this value for any gate-to-source voltage Ves GS V DS (volts)

Tabulate the values as shown below. VGs Volts) VDSa) (Volts) 0 0 0.4 0 0.8 0.4 1.25 0.85 1.6 0.85 0.85 2 2.2 0.85 2.4 0.85 0.85 2.6 2.8 0.85 0.85 3.0 Plot V DS( over the range 0Vs3 as shown below GS 0.9 0,8 F 0.7 F 0.6 F 0.5 0.4 F 0.3 0.2 F 0.1 0 0.5 5 2 2.5 3 V GS (volts) OC N ni V DS (volts)