Your team’s task for this project is to simulate an NMOStransistor, compute the DC operating point and then design a biasnetwork to properly operate the transistor in saturation. Thetransistor you will use is described by the spice model below:

ltSPICE:

.modelNMOS0P5              NMOS(Level=1 VTO=0.7 GAMMA=0.5 PHI=0.8

+                             LD=0.08E-06 WD=0 UO=460 LAMBDA=0.001 TOX=9.5E-9 PB=0.9CJ=0.57E-3

+                             CJSW=120E-12 MJ=0.5 MJSW=0.4 CGDO=0.4E-9 JS=10E-9 CGBO=0.38E-9

+                             CGSO=0.4E-9)

MultiSim:

.SUBCKT NMOS0P5 1 2 3 4

M 1 2 3 4 NMOS0P5 W=5u L=0.5u

.modelNMOS0P5              NMOS(Level=1 VTO=0.7 GAMMA=0.5 PHI=0.8

+                             LD=0.08E-06 WD=0 UO=460 LAMBDA=0.001 TOX=9.5E-9 PB=0.9CJ=0.57E-3

+                             CJSW=120E-12 MJ=0.5 MJSW=0.4 CGDO=0.4E-9 JS=10E-9 CGBO=0.38E-9

+                             CGSO=0.4E-9)

.ENDS NMOS0P5

In ltSPICE use the NMOS4 schematic component and a SPICEdirective to properly load your model. In multisim use thecomponent wizard and the MOS_N_4T schematic component. (see Figure1 for proper multisim component creation). If you are usingmultisim.com online simulator, simply use a ‘NMOS’ device and inputthe Vt, Kn’ (shown as Kp) and W/L in the right sidemenu.

Figure 1. Custom component model

NOTE: for NMOS4 and MOS_N_4T you must connect the base to yoursource terminal as seen in Figure 3.

Figure 2. NMOS4 component

For the first part, you are to use the saturation equation foran NMOS with a Vt = 0.7V, K_n’ of 2.469 x10^-4and a W/L of 10 (use 0.5u for L 5u for W in yoursimulation) to get a I_D of 4 mA. Once you findyou V_OV value solve for your V_GS. Once yourhave your V_GS simulate the I/V curve you are familiarwith using DC sweep on V_DS (start at 0V finishat 5V with 0.5V steps) and a fixed V_gs that youfound using your equation. If you are using multisim.comyou can simply show a transient line graph of 4mA Id.

For the second part, you are to find resistor values in theconfiguration shown in figure 3 to achieve the V_GS yousolved for analytically in part 1 (use resistors in the100k-1000 kOhm range for R_G1-2) as well as aV_D of 3V so that the transistor is operating insaturation. (use the DC operating point simulation to findthese values, use V_DD = 5V).

Lastly, if we are to operate this transistor in deep triode,what is the resistor value r_ds?

Figure 3. Classical bias NMOS configuration

In summary:

Find V_GS analytically

Graph the I/V curve at this V_GS using DC Sweep

Find R_G1 R_G2 and R_D for aV_D of 3V

Show the DC Operating Point in saturation

Find r_ds analytically