Find the operating modes for the nMOSFET circuit in Fig. 4a and its complementary pMOSFET
circuit in Fig. 4b, for switching operation. Note that Fig. 4a is a similar circuit given in Figure 5.
27 in [1] except vDS = v0 - Vs and vcs = v, - Vs. Show that the operating mode of the
nMOSFET in Fig. 4a switches from cut-off to triode (linear) if V/ level is switched from -1. 8 V
to +1. 8 V. Calculate v0 for both cases. Show that the operating mode of the pMOSFET in Fig.
4b switches in the other direction from triode (linear) to cut-off if v, level is switched from -1. 8
V to +1. 8 V. Calculate vQ for both cases. Fig. 4c is a CMOS digital inverter circuit. It is made
by joining the two circuits in Fig. 4a and Fig. 4b together. Find and plot v0(t) if Vj(t) is a digital
signal with low and high levels as shown in Fig. 4c.
Solution
for a nmosfet
if Vgs < Vt , it is in cut off mode
if Vgs > Vt, it is in triode region
for Vi = -1.8, Vgs = Vi - Vs = -1.8 -(-1.8) = 0
Vgs < Vt so it is in cut off
for Vi = 1.8 , Vgs = 1.8 - (-1.8) = 3.6V
Vgs >Vt so it is in triode region.
In cut off mode Vo = 0V
and in triode region, Vo = - Id(12K)
Id = Kn * [(Vgs-Vt)(Vo-Vs) - (Vo-Vs)2 /2]
-Vo / 12 = 0.8 * [3.1(Vo +1.8) - 0.5(Vo +1.8)2]
soving this quadratic we get Vo at Vi = 1.8V
**********************************************************************
for a pmosfet
if Vgs < Vt , it is in linear mode
if Vgs > Vt, it is in cutoff region
for Vi = -1.8, Vgs = Vi - Vs = -1.8 -(1.8) = -3.6
Vgs < Vt so it is in triode region
for Vi = 1.8 , Vgs = 1.8 - (1.8) = 0V
Vgs >Vt so it is in cut off region.
In cut off mode Vo = 0V
and in triode region, Vo = Id(12K)
Id = Kp * [(Vgs-Vt)(Vo-Vs) - (Vo-Vs)2 /2]
Vo / 12 = 0.8 * [-3.6(Vo -1.8) - 0.5(Vo -1.8)2]
soving this quadratic we get Vo at Vi = -1.8V.
Find the operating modes for the nMOSFET circuit in Fig. 4a and its c.pdf
1. Find the operating modes for the nMOSFET circuit in Fig. 4a and its complementary pMOSFET
circuit in Fig. 4b, for switching operation. Note that Fig. 4a is a similar circuit given in Figure 5.
27 in [1] except vDS = v0 - Vs and vcs = v, - Vs. Show that the operating mode of the
nMOSFET in Fig. 4a switches from cut-off to triode (linear) if V/ level is switched from -1. 8 V
to +1. 8 V. Calculate v0 for both cases. Show that the operating mode of the pMOSFET in Fig.
4b switches in the other direction from triode (linear) to cut-off if v, level is switched from -1. 8
V to +1. 8 V. Calculate vQ for both cases. Fig. 4c is a CMOS digital inverter circuit. It is made
by joining the two circuits in Fig. 4a and Fig. 4b together. Find and plot v0(t) if Vj(t) is a digital
signal with low and high levels as shown in Fig. 4c.
Solution
for a nmosfet
if Vgs < Vt , it is in cut off mode
if Vgs > Vt, it is in triode region
for Vi = -1.8, Vgs = Vi - Vs = -1.8 -(-1.8) = 0
Vgs < Vt so it is in cut off
for Vi = 1.8 , Vgs = 1.8 - (-1.8) = 3.6V
Vgs >Vt so it is in triode region.
In cut off mode Vo = 0V
and in triode region, Vo = - Id(12K)
Id = Kn * [(Vgs-Vt)(Vo-Vs) - (Vo-Vs)2 /2]
-Vo / 12 = 0.8 * [3.1(Vo +1.8) - 0.5(Vo +1.8)2]
soving this quadratic we get Vo at Vi = 1.8V
**********************************************************************
for a pmosfet
if Vgs < Vt , it is in linear mode
if Vgs > Vt, it is in cutoff region
for Vi = -1.8, Vgs = Vi - Vs = -1.8 -(1.8) = -3.6
Vgs < Vt so it is in triode region
for Vi = 1.8 , Vgs = 1.8 - (1.8) = 0V
Vgs >Vt so it is in cut off region.
In cut off mode Vo = 0V
and in triode region, Vo = Id(12K)
Id = Kp * [(Vgs-Vt)(Vo-Vs) - (Vo-Vs)2 /2]
Vo / 12 = 0.8 * [-3.6(Vo -1.8) - 0.5(Vo -1.8)2]
![Find the operating modes for the nMOSFET circuit in Fig. 4a and its complementary pMOSFET
circuit in Fig. 4b, for switching operation. Note that Fig. 4a is a similar circuit given in Figure 5.
27 in [1] except vDS = v0 - Vs and vcs = v, - Vs. Show that the operating mode of the
nMOSFET in Fig. 4a switches from cut-off to triode (linear) if V/ level is switched from -1. 8 V
to +1. 8 V. Calculate v0 for both cases. Show that the operating mode of the pMOSFET in Fig.
4b switches in the other direction from triode (linear) to cut-off if v, level is switched from -1. 8
V to +1. 8 V. Calculate vQ for both cases. Fig. 4c is a CMOS digital inverter circuit. It is made
by joining the two circuits in Fig. 4a and Fig. 4b together. Find and plot v0(t) if Vj(t) is a digital
signal with low and high levels as shown in Fig. 4c.
Solution
for a nmosfet
if Vgs < Vt , it is in cut off mode
if Vgs > Vt, it is in triode region
for Vi = -1.8, Vgs = Vi - Vs = -1.8 -(-1.8) = 0
Vgs < Vt so it is in cut off
for Vi = 1.8 , Vgs = 1.8 - (-1.8) = 3.6V
Vgs >Vt so it is in triode region.
In cut off mode Vo = 0V
and in triode region, Vo = - Id(12K)
Id = Kn * [(Vgs-Vt)(Vo-Vs) - (Vo-Vs)2 /2]
-Vo / 12 = 0.8 * [3.1(Vo +1.8) - 0.5(Vo +1.8)2]
soving this quadratic we get Vo at Vi = 1.8V
**********************************************************************
for a pmosfet
if Vgs < Vt , it is in linear mode
if Vgs > Vt, it is in cutoff region
for Vi = -1.8, Vgs = Vi - Vs = -1.8 -(1.8) = -3.6
Vgs < Vt so it is in triode region
for Vi = 1.8 , Vgs = 1.8 - (1.8) = 0V
Vgs >Vt so it is in cut off region.
In cut off mode Vo = 0V
and in triode region, Vo = Id(12K)
Id = Kp * [(Vgs-Vt)(Vo-Vs) - (Vo-Vs)2 /2]
Vo / 12 = 0.8 * [-3.6(Vo -1.8) - 0.5(Vo -1.8)2]](https://image.slidesharecdn.com/findtheoperatingmodesforthenmosfetcircuitinfig-230325070335-657f8151/85/Find-the-operating-modes-for-the-nMOSFET-circuit-in-Fig-4a-and-its-c-pdf-1-320.jpg)
