Electronics I (Devices and Materials)
Project 2: NMOS DC Operation in Saturation
Your task for this project is to simulate an NMOS transistor, compute the DC operating point and then design a bias network to properly operate the transistor in
saturation. The transistor you will use is described by the spice model below:
ltSPICE:
.model NMOS0P5 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=0.9 CJ=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
.model NMOS0P5 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=0.9 CJ=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 SPICE directive to properly load your model. In multisim use the component wizard and the MOS_N_4T schematic
component. (see Figure 1 for proper multisim component creation)
Figure 1. Custom component model
NOTE: for NMOS4 and MOS_N_4T you must connect the base to your source terminal as seen in Figure 3.
Figure 2. NMOS4 component
For the first part, you are to use the saturation equation for an NMOS with a Kn’ of 1.234 x10-4 and a W/L of 10 (use 0.5u for L 5u for W in your simulation) to get a
ID of 4 mA. Once you find you VOV value solve for your VGS. Once your have your VGS simulate the I/V curve you are familiar with using DC sweep on VDS (start at 0V
finish at 5V with 0.5V steps) and a fixed Vgs that you found using your equation.
For the second part, you are to find resistor values in the configuration shown in figure 3 to achieve the VGS you solved for analytically in part 1 (use resistors in
the 100-1000 kOhm range for RG1-2) as well as a VD of 3V so that the transistor is operating in saturation. (use the DC operating point simulation to find these
values, use VDD = 5V).
Lastly, if we are to operate this transistor in deep triode, what is the resistor value rds?
