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Electronic Devices and Circuit Theory

Robert Boylestad, Louis Nashelsky

Chapter 6

Field-Effect Transistors - all with Video Answers

Educators

Chapter Questions

01:13

Problem 1

a. Draw the basic construction of a $p$ -channel JFET.
b. Apply the proper biasing between drain and source and sketch the depletion region for $V_{G S}=0 \mathrm{~V}$

Chai Santi
Chai Santi
Numerade Educator
06:36

Problem 2

Using the characteristics of Fig. 11, determine $I_{D}$ for the following levels of $V_{G S}$ (with $\left.V_{D S}>V_{P}\right):$
a. $V_{G S}=0 \mathrm{~V}$.
b. $V_{G S}=-1 \mathrm{~V}$.
c. $V_{G S}=-1.5 \mathrm{~V}$.
d. $V_{G S}=-1.8 \mathrm{~V}$.
e. $V_{G S}=-4 \mathrm{~V}$.
f. $V_{G S}=-6 \mathrm{~V}$.

Thomas Thompson
Thomas Thompson
Numerade Educator
05:10

Problem 3

Using the results of problem 2 plot the transfer characteristics of $I_{D}$ vs. $V_{G S}$

Arpit Gupta
Arpit Gupta
Numerade Educator
01:13

Problem 4

a. Determine $V_{D S}$ for $V_{G S}=0 \mathrm{~V}$ and $I_{D}=6 \mathrm{~mA}$ using the characteristics of Fig. 11 .
b. Using the results of part (a), calculate the resistance of the JFET for the region $I_{D}=0$ to $6 \mathrm{~mA}$ for $V_{G S}=0 \mathrm{~V}$
c. Determine $V_{D S}$ for $V_{G S}=-1 \mathrm{~V}$ and $I_{D}=3 \mathrm{~mA}$.
d. Using the results of part (c), calculate the resistance of the JFET for the region $I_{D}=0$ to $3 \mathrm{~mA}$ for $V_{G S}=-1 \mathrm{~V}$
e. Determine $V_{D S}$ for $V_{G S}=-2 \mathrm{~V}$ and $I_{D}=1.5 \mathrm{~mA}$.
f. Using the results of part (e), calculate the resistance of the JFET for the region $I_{D}=0$ to $1.5 \mathrm{~mA}$ for $V_{G S}=-2 \mathrm{~V}$
g. Defining the result of part (b) as $r_{o}$, determine the resistance for $V_{G S}=-1 \mathrm{~V}$ using Eq. (1) and compare with the results of part (d).
h. Repeat part $(\mathrm{g})$ for $V_{G S}=-2 \mathrm{~V}$ using the same equation, and compare the results with part (f).
i. Based on the results of parts (g) and (h), does Eq. (1) appear to be a valid approximation?

Chai Santi
Chai Santi
Numerade Educator
02:01

Problem 5

Using the characteristics of Fig. 11 :
a. Determine the difference in drain current (for $V_{D S}>V_{P}$ ) between $V_{G S}=0 \mathrm{~V}$ and $V_{G S}=-1 \mathrm{~V}$.
b. Repeat part (a) between $V_{G S}=-1$ and $-2 \mathrm{~V}$.
c. Repeat part
(a) between $V_{G S}=-2$ and $-3 \mathrm{~V}$.
d. Repeat part (a) between $V_{G S}=-3$ and $-4 \mathrm{~V}$.
e. Is there a marked change in the difference in current levels as $V_{G S}$ becomes increasingly negative?
f. Is the relationship between the change in $V_{G S}$ and the resulting change in $I_{D}$ linear or nonlinear? Explain.

Khoobchandra Agrawal
Khoobchandra Agrawal
Numerade Educator
01:13

Problem 6

What are the major differences between the collector characteristics of a BJT transistor and the drain characteristics of a JFET transistor? Compare the units of each axis and the controlling variable. How does $I_{C}$ react to increasing levels of $I_{B}$ versus changes in $I_{D}$ to increasingly negative values of $V_{G S}$ ? How does the spacing between steps of $I_{B}$ compare to the spacing between steps of $V_{G S}$ ? Compare $V_{C_{\text {st }}}$ to $V_{P}$ in defining the nonlinear region at low levels of output voltage.

Chai Santi
Chai Santi
Numerade Educator
01:43

Problem 7

a. Describe in your own words why $I_{G}$ is effectively $0 \mathrm{~A}$ for a JFET transistor.
b. Why is the input impedance to a JFET so high?
c. Why is the terminology field effect appropriate for this important three-terminal device?

Penny Riley
Penny Riley
Numerade Educator
02:18

Problem 8

Given $I_{D S S}=12 \mathrm{~mA}$ and $\left|V_{P}\right|=6 \mathrm{~V}$, sketch a probable distribution of characteristic curves for the JFET (similar to Fig. 11).

Chai Santi
Chai Santi
Numerade Educator
01:13

Problem 9

In general, comment on the polarity of the various voltages and direction of the currents for an $n$ -channel JFET versus a $p$ -channel JFET.

Chai Santi
Chai Santi
Numerade Educator
17:36

Problem 10

Given the characteristics of Fig. 54 :
a. Sketch the transfer characteristics directly from the drain characteristics.
b. Using Fig. 54 to establish the values of $I_{D S S}$ and $V_{P}$, sketch the transfer characteristics using Shockley's equation.
c. Compare the characteristics of parts (a) and (b). Are there any major differences?

Paul A.
Paul A.
California State Polytechnic University, Pomona
02:04

Problem 11

a. Given $I_{D S S}=12 \mathrm{~mA}$ and $V_{P}=-4 \mathrm{~V}$, sketch the transfer characteristics for the JFET transistor.
b. Sketch the drain characteristics for the device of part (a).

Chai Santi
Chai Santi
Numerade Educator
01:46

Problem 12

Given $I_{D S S}=9 \mathrm{~mA}$ and $V_{P}=-4 \mathrm{~V}$, determine $I_{D}$ when:
a. $V_{G S}=0 \mathrm{~V}$.
b. $V_{G S}=-2 \mathrm{~V}$.
c. $V_{G S}=-4 \mathrm{~V}$.
d. $V_{G S}=-6 \mathrm{~V}$.

Subhakanta Sahoo
Subhakanta Sahoo
Numerade Educator
01:27

Problem 13

Given $I_{D S S}=16 \mathrm{~mA}$ and $V_{P}=-5 \mathrm{~V}$, sketch the transfer characteristics using the data points of Table 1. Determine the value of $I_{D}$ at $V_{G S}=-3 \mathrm{~V}$ from the curve, and compare it to the value determined using Shockley's equation. Repeat the above for $V_{G S}=-1 \mathrm{~V}$.

Eric Mockensturm
Eric Mockensturm
Numerade Educator
03:36

Problem 14

For a particular JFET if $I_{D}=4 \mathrm{~mA}$ when $V_{G S}=-3 \mathrm{~V}$, determine $V_{P}$ if $I_{D S S}=12 \mathrm{~mA}$.

Arpit Gupta
Arpit Gupta
Numerade Educator
05:33

Problem 15

Given $I_{D S S}=6 \mathrm{~mA}$ and $V_{P}=-4.5 \mathrm{~V}$
a. Determine $I_{D}$ at $V_{G S}=-2$ and $-3.6 \mathrm{~V}$.
b. Determine $V_{G S}$ at $I_{D}=3$ and $5.5 \mathrm{~mA}$.

ES
Ellie Sun
Numerade Educator
02:35

Problem 16

Given a $Q$ -point of $I_{D_{Q}}=3 \mathrm{~mA}$ and $V_{G S}=-3 \mathrm{~V}$, determine $I_{D S S}$ if $V_{P}=-6 \mathrm{~V}$.

Frank Lin
Frank Lin
Numerade Educator
02:10

Problem 17

A $p$ -channel JFET has device parameters of $I_{D S S}=7.5 \mathrm{~mA}$ and $V_{P}=4 \mathrm{~V}$. Sketch the transfer characteristics.

Susan Hallstrom
Susan Hallstrom
Numerade Educator
03:08

Problem 18

Define the region of operation for the $2 \mathrm{~N} 5457$ JFET of Fig. 20 using the range of $I_{D S S}$ and $V_{P}$ provided. That is, sketch the transfer curve defined by the maximum $I_{D S S}$ and $V_{P}$ and the transfer curve for the minimum $I_{D S S}$ and $V_{P}$. Then, shade in the resulting area between the two curves.

Finn Hittson
Finn Hittson
Numerade Educator
02:22

Problem 19

For the 2N5457 JFET of Fig. 20, what is the power rating at a typical operating temperature of $45^{\circ} \mathrm{C}$ using the $5.0 \mathrm{~mW} /{ }^{\circ} \mathrm{C}$ derating factor.

Manish Haldankar
Manish Haldankar
Numerade Educator
02:58

Problem 20

Define the region of operation for the JFET of Fig. 54 if $V_{D S_{\max }}=30 \mathrm{~V}$ and $P_{D_{\max }}=100 \mathrm{~mW}$.

Chai Santi
Chai Santi
Numerade Educator
03:20

Problem 21

Using the characteristics of Fig. 22, determine $I_{D}$ at $V_{G S}=-0.7 \mathrm{~V}$ and $V_{D S}=10 \mathrm{~V}$.

Vishal Gupta
Vishal Gupta
Numerade Educator
02:13

Problem 22

Referring to Fig. 22 , is the locus of pinch-off values defined by the region of $V_{D S}<\left|V_{P}\right|=3 \mathrm{~V}$ ?

Dorcas Attuabea Addo
Dorcas Attuabea Addo
Numerade Educator
03:45

Problem 23

Determine $V_{P}$ for the characteristics of Fig. 22 using $I_{D S S}$ and $I_{D}$ at some value of $V_{G S}$. That is, simply substitute into Shockley's equation and solve for $V_{P}$. Compare the result to the assumed value of $-3 \mathrm{~V}$ from the characteristics.

Narayan Hari
Narayan Hari
Numerade Educator
03:45

Problem 24

Using $I_{D S S}=9 \mathrm{~mA}$ and $V_{P}=-3 \mathrm{~V}$ for the characteristics of Fig. 22, calculate $I_{D}$ at $V_{G S}=$ $-1$ V using Shockley's equation and compare to the level in Fig. 22 .

Narayan Hari
Narayan Hari
Numerade Educator
02:07

Problem 25

a. Calculate the resistance associated with the JFET of Fig. 22 for $V_{G S}=0 \mathrm{~V}$ from $I_{D}=0 \mathrm{~mA}$ to $4 \mathrm{~mA}$.
b. Repeat part (a) for $V_{G S}=-0.5 \mathrm{~V}$ from $I_{D}=0$ to $3 \mathrm{~mA}$.
c. Assigning the label $r_{o}$ to the result of part (a) and $r_{d}$ to that of part (b), use Eq. (1) to determine $r_{d}$ and compare to the result of part (b).

Sanjeev Kumar
Sanjeev Kumar
Numerade Educator
01:05

Problem 26

a. Sketch the basic construction of a $p$ -channel depletion-type MOSFET.
b. Apply the proper drain-to-source voltage and sketch the flow of electrons for $V_{G S}=0 \mathrm{~V}$.

Chai Santi
Chai Santi
Numerade Educator
00:39

Problem 27

In what ways is the construction of a depletion-type MOSFET similar to that of a JFET? In what ways is it different?

Manish Kumar
Manish Kumar
Numerade Educator
01:00

Problem 28

Explain in your own words why the application of a positive voltage to the gate of an $n$ -channel depletion-type MOSFET will result in a drain current exceeding $I_{D S S}$.

Chai Santi
Chai Santi
Numerade Educator
01:36

Problem 29

Given a depletion-type MOSFET with $I_{D S S}=6 \mathrm{~mA}$ and $V_{P}=-3 \mathrm{~V}$, determine the drain current at $V_{G S}=-1,0,1$, and $2 \mathrm{~V}$. Compare the difference in current levels between $-1 \mathrm{~V}$ and $0 \mathrm{~V}$ with the difference between $1 \mathrm{~V}$ and $2 \mathrm{~V}$. In the positive $V_{G S}$ region, does the drain current increase at a significantly higher rate than for negative values? Does the $I_{D}$ curve become more and more vertical with increasing positive values of $V_{G S} ?$ Is there a linear or a nonlinear relationship between $I_{D}$ and $V_{G S}$ ? Explain.

Chai Santi
Chai Santi
Numerade Educator
01:33

Problem 30

Sketch the transfer and drain characteristics of an $n$ -channel depletion-type MOSFET with $I_{D S S}=12 \mathrm{~mA}$ and $V_{P}=-8 \mathrm{~V}$ for a range of $V_{G S}=-V_{P}$ to $V_{G S}=1 \mathrm{~V}$.

Chai Santi
Chai Santi
Numerade Educator
01:03

Problem 31

Given $I_{D}=14 \mathrm{~mA}$ and $V_{G S}=1 \mathrm{~V}$, determine $V_{P}$ if $I_{D S S}=9.5 \mathrm{~mA}$ for a depletion-type MOSFET.

Chai Santi
Chai Santi
Numerade Educator
02:02

Problem 32

Given $I_{D}=4 \mathrm{~mA}$ at $V_{G S}=-2 \mathrm{~V}$, determine $I_{D S S}$ if $V_{P}=-5 \mathrm{~V}$.

Sanchit Jain
Sanchit Jain
Numerade Educator
01:36

Problem 33

Using an average value of $2.9 \mathrm{~mA}$ for the $I_{D S S}$ of the 2N3797 MOSFET of Fig. 31 , determine the level of $V_{G S}$ that will result in a maximum drain current of $20 \mathrm{~mA}$ if $V_{P}=-5 \mathrm{~V}$.

Chai Santi
Chai Santi
Numerade Educator
01:46

Problem 34

If the drain current for the 2N3797 MOSFET of Fig. 31 is $8 \mathrm{~mA}$, what is the maximum permissible value of $V_{D S}$ utilizing the maximum power rating?

Chai Santi
Chai Santi
Numerade Educator
03:08

Problem 35

a. What is the significant difference between the construction of an enhancement-type MOSFET and a depletion-type MOSFET?
b. Sketch a $p$ -channel enhancement-type MOSFET with the proper biasing applied $\left(V_{D S}>0 \mathrm{~V}, V_{G S}>V_{T}\right)$ and indicate the channel, the direction of electron flow, and the resulting depletion region.
c. In your own words, briefly describe the basic operation of an enhancement-type MOSFET.

Chai Santi
Chai Santi
Numerade Educator
01:08

Problem 36

a. Sketch the transfer and drain characteristics of an $n$ -channel enhancement-type MOSFET if $V_{T}=3.5 \mathrm{~V}$ and $k=0.4 \times 10^{-3} \mathrm{~A} / \mathrm{V}^{2}$
b. Repeat part (a) for the transfer characteristics if $V_{T}$ is maintained at $3.5 \mathrm{~V}$ but $k$ is increased by $100 \%$ to $0.8 \times 10^{-3} \mathrm{~A} / \mathrm{V}^{2}$.

Chai Santi
Chai Santi
Numerade Educator
04:38

Problem 37

a. Given $V_{G S(\mathrm{Th})}=4 \mathrm{~V}$ and $I_{D(\mathrm{on})}=4 \mathrm{~mA}$ at $V_{G S(\mathrm{on})}=6 \mathrm{~V}$, determine $k$ and write the general expression for $I_{D}$ in the format of Eq. (15).
b. Sketch the transfer characteristics for the device of part (a).
c. Determine $I_{D}$ for the device of part (a) at $V_{G S}=2,5$, and $10 \mathrm{~V}$.

Arpit Gupta
Arpit Gupta
Numerade Educator
02:35

Problem 38

Given the transfer characteristics of Fig. 55, determine $V_{T}$ and $k$ and write the general equation for $I_{D}$.

Yujie Wang
Yujie Wang
College of San Mateo
01:01

Problem 39

Given $k=0.4 \times 10^{-3} \mathrm{~A} / \mathrm{V}^{2}$ and $I_{D(\mathrm{on})}=3 \mathrm{~mA}$ with $V_{G S(\mathrm{on})}=4 \mathrm{~V}$, determine $V_{T}$

Linh Vu
Linh Vu
Numerade Educator
02:18

Problem 40

The maximum drain current for the 2N4351 $n$ -channel enhancement-type MOSFET is $30 \mathrm{~mA}$. Determine $V_{G S}$ at this current level if $k=0.06 \times 10^{-3} \mathrm{~A} / \mathrm{V}^{2}$ and $V_{T}$ is the maximum value.

Chai Santi
Chai Santi
Numerade Educator
01:35

Problem 41

Does the current of an enhancement-type MOSFET increase at about the same rate as a depletiontype MOSFET for the conduction region? Carefully review the general format of the equations, and if your mathematics background includes differential calculus, calculate $d I_{D} / d V_{G S}$ and compare its magnitude.

Chai Santi
Chai Santi
Numerade Educator
02:18

Problem 42

Sketch the transfer characteristics of a $p$ -channel enhancement-type MOSFET if $V_{T}=-5 \mathrm{~V}$ and $k=0.45 \times 10^{-3} \mathrm{~A} / \mathrm{V}^{2}$.

Chai Santi
Chai Santi
Numerade Educator
04:13

Problem 43

Sketch the curve of $I_{D}=0.5 \times 10^{-3}\left(V_{G S}^{2}\right)$ and $I_{D}=0.5 \times 10^{-3}\left(V_{G S}-4\right)^{2}$ for $V_{G S}$ from $0 \mathrm{~V}$ to $10 \mathrm{~V}$. Does $V_{T}=4 \mathrm{~V}$ have a significant effect on the level of $I_{D}$ for this region?

Chris Trentman
Chris Trentman
Numerade Educator
01:24

Problem 44

a. Describe in your own words why the VMOS FET can withstand a higher current and power rating than devices constructed with standard techniques.
b. Why do VMOS FETs have reduced channel resistance levels?
c. Why is a positive temperature coefficient desirable?

Ajay Singhal
Ajay Singhal
Numerade Educator
03:00

Problem 45

What are the relative advantages of the UMOS technology over the VMOS technology?

Ajay Singhal
Ajay Singhal
Numerade Educator
02:34

Problem 46

a. Describe in your own words the operation of the network of Fig. 45 with $V_{i}=0 \mathrm{~V}$.
b. If the "on" MOSFET of Fig. 45 (with $V_{i}=0 \mathrm{~V}$ ) has a drain current of $4 \mathrm{~mA}$ with $V_{D S}=0.1 \mathrm{~V}$, what is the approximate resistance level of the device? If $I_{D}=0.5 \mu \mathrm{A}$ for the "off" transistor, what is the approximate resistance of the device? Do the resulting resistance levels suggest that the desired output voltage level will result?

Chai Santi
Chai Santi
Numerade Educator
01:13

Problem 47

Research CMOS logic at your local or college library, and describe the range of applications and basic advantages of the approach.

Hunza Gilgit
Hunza Gilgit
Numerade Educator