Applications of MOS Transistors in Digital Integrated Circuits (1) Section 15.1

ADD an Instance of NMOS NMOS transistor

A Simple Switching Circuit variable DC voltage

Threhold Voltage Threshold voltage of T0

Design variable Library Setup

A Primitive Inverter Circuit Large VDS SATURATION Small VDS :Triode

Determine Region of Operation OFF SATURATION TRIODE

Determine Kn and Vth Need to select drain terminal in order to get current

Derivation ID=0.5 unCox(W/L)(VGS-VTH)2 Find VTH SQRT(2ID/(unCoxW/L))=VGS-VTH The VGS that yields 0 LHS is the threshold voltage SQRT(ID)=SLOPE(VGS-VTH) SLOPE=SQRT(0.5 unCox(W/L)) This example: W/L=2um/1um=2 SLOPE=SQRT(unCox)

To Calculate Kn,find SQRT(ID) The x interscept gives Vth Vth (this method)=150 mV Vth(Cadence)=164 mV

Find Kn=W/LunCox SQRT(ID) dSQRT(ID)/dVGS This curve implies that unCox depends on VGS!

Noise Margin Noise Margin: the maximum amount of noise at the input that can be tolerated before the output is affected significantly. attenuating attenuating amplifying dVout/dVGS NML NMH dVout/dVGS=small signal gain

Generate Random Noise in Matlab

Inverter In the Presence of Noise Relatively clean output 400 mV peak to peak noise Time Scaling Factor

Inverter In the Presence of More Noise 1 V peak to peak of noise

Noisy Input Relatively Clean Output

Adding a Capacitor to the Output RC time constant

Ring Oscillator 1nF oscillation

Ring Oscillator with Output Capacitor Load of 10 nF