Malvino Problems.docx

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Malvino Problems

CHAPTER 1|Introduction

1. A circuit has a Norton current of 10mA and a Norton

resistance of 10kΩ. What is the Thevenin circuit?

2. A current source has an internal resistance of 100kΩ.

What is the largest load resistance if the current

source must appear stiff?

3. Suppose a current source has an ideal current of 10

mA and an internal resistance of 20 MΩ. For what

values of load resistance will the current source

appear stiff?

4. The internal resistance of a voltage source equals

0.05 ohms. How much voltage is dropped across this

internal resistance when the current through it

equals 2A?

5. A flashlight battery has an internal reistance of 1Ω.

For what values of load resistance does the flashlight

battery appear stiff?

6. Suppose a voltage source has an ideal voltage of 12

V and an internal resistance of 0.5Ωor what values of

load resistance will the voltage source appear stiff?

CHAPTER 2|Semiconductors

1. What is the net charge of a copper atom if it gains

three electrons?

2. A silicon diode has a saturation current of 10 nA at

25 C. If it operates over a temperature range of 0 to

75 C, what are the minimum and maximum values of

saturation current?

3. A silicon diode has a reverse current of 5µA at 25 C

and 100 µA at 100C. What are the values of thesaturation current and the surface leakage current at

25C?

4. A silicon diode has a saturation current of 5 nA at 25

C. What is the saturation current at 100C?

5. If the surface leakage current is 2nA for a reverse

voltage of 25 V, what is the surface leakage current

for a reverse voltage of 35?

6. Assuming a barrier potential of 0.7 V at an ambient

temperature of 25C, what is the barrier potential of

a silicon diode when the junction temperature is

100C? at 0C?

CHAPTER 3|Diode Theory

1. A diode is in series with 220 Ω. If the voltage across

the resistor is 4V, what is the current through the

diode?

2. Two diodes are in series. The first diode has a

voltage of 0.75 V and the second has a voltage of 0.8

V. If the current through first diode is 500 mA, what

is the current through the second diode?

CHAPTER 4|Diode Circuits

1. A half-wave signal with a peak of 20 V is the input to

a choke-input filter. If XL = 5kΩ and XC = 25 Ω, what is

the approximate peak to peak ripple across the

capacitor?

2. A center-tapped transformer has a turns ratio of 6:1.

What is the rms voltage across the ipper half of the

secondary winding? The peak voltage? What is the

rms voltage across the lower half of the secondary

winding?

3. If a transformer has a turns ratio of 15:1, what is the

rms secondary voltage? The peak secondary

voltage? Assume a primary voltage of 120 Vrms.

CHAPTER 5|Special purpose diodes

1. An unloaded zener regulator has a source voltage of

20V, a series resistance of 330 Ω, and a zener voltageof 12 V. What is the zener current?

2. If the series resistor in (1) has a tolerance of ±10

percent, what is the maximum zener current?

3. A zener diode has a voltage of 10 V and a current of

20 mA. What is the power dissipation?

4. A zener regulator has an input voltage that may vary

from 22 to 30 V. If the regulated output voltage is

12V and the load resistance varies from 140Ω to 10kΩ, what is the maximum allowable series

resistance?

CHAPTER 6|BJTs

1. A 2N5067 is a power transistor with a base bulk

resistance rb’ of 10Ω. How much IBrb’ drop is there

when IB = 1 mA? When IB = 10 mA? When IB = 50

mA?

2. What is the current gain of a transistor with a dc

alpha of 0.994?

3. A transistor has a power rating of 1 W. If the

collector-emitter voltage is 10V and the collector

current is 120 mA, what happens to the transistor?



4. If a transistor has a collector current of 100 mA and a

collector emitter voltage of 3.5 V, what is its power

dissipation?

5. A transistor has a current gain of 125 and a base

current of 30µA. What is the collector current?

6. A transistor has an emitter current of 10 mA and a

collector current of 9.95 mA. What is the base

current?

CHAPTER 9|AC Models

1. If an ac base current of 50µA produces an ac

collector current of 7.5mA, what is the ac beta?

2. If the ac collector current is 4 mA and the ac beta is

300, what is the ac base current?

CHAPTER 11|POWER AMPLIFIERS

1. An amplifier has an input power of 4 mW and output

power of 2 W. What is the power gain?

CHAPTER 13|JFETs

1. A 2N4416 has IDSS = 10 mA and gm0 = 4000 µS. What

is its gate-source cut off voltage? What is the valueof gm0 for VGS = -2V?

2. A 2N5670 has IDSS = 12 mA and VGS(OFF) = -3 V. What

are the gate voltage and drain current at the half

cutoff point?

3. A 2N5457 has IDSS = 1 to 5 mA and VGS(OFF) = -0.5 to -6

V. What are the minimum and maximum values of

RDS?

4. A JFET has IDSS = 16 mA and Vp = 3 V. What is the

maximum drain current? The gate-source cutoff

voltage? The value of RDS?

5. A 2N5458 has a gate current of 1 nA when the

reverse voltage is -20V. What is the input resistance

of the gate?

6. A JFET shunt switch has RD = 10 kΩ, IDSS = 10 mA, and

VGS(OFF) = -2 V. If vin = 10 mV pp, what are the output

voltages? What is the on-off ratio?

CHAPTER 14|MOSFETs

1. An E-MOSFET has these values: ID(active) = 1 mA and

VDS(active) = 10 V. What does its drain resistance equal

in the active region?

CHAPTER 16|Frequency Effects

1. You have two data sheets for amplifiers. The first

shows a cutoff frequency of 1 MHz. The second gives

a risetime of 1 µs. Which amplifier has the greater

bandwidth?

2. What is the bandwidth of an amplifier if the risetime

is 0.25µs?

3. Convert the following powers to dBm: 25 mW, 93.5

mW, 4.87 W.

4. If the output power of a preamplifier is 16 dBm, how

much power is this in milliwatts?

5. The data sheet of an LM380, an audio power

amplifier, gives a decibel voltage gain of 34 dB.

Convert this to ordinary voltage gain.

6. A dc amplifier has a midband voltage gain of 100. If

the upper cutoff frequency is 10 kHz, what is the

voltage gain for each of these input frequencies: 100

kHz, 200 kHz, 500 kHz, and 1 MHz?

7. An amplifier has a midband voltage gain of 1000. If

cutoff frequencies are f 1 = 100 Hz, and f 2 = 100 kHz,

what does the frequency response look like? What is

the voltage gain if the input frequency is 20 Hz? If it

is 300 kHz?

CHAPTER 17|Differential Amplifiers

1. A 741 is an op amp with A = 200,000 and CMRR dB =

90 dB. What is the common-mode voltage gain? If

the desired and common-mode signal each has a

value of 1 µV, what is the output voltage?

CHAPTER 18|Operational Amplifiers

1.

What is the CMRR of a 741C at 100 kHz? The MPPvalue when the load resistance is 500 Ω? The open

loop voltage gain at 1 kHz?

2. What is the initial slope of a sine wave with a

frequency of 15 kHz and a peak value of 2 V? What

happens to the initial slope if the frequency

increases to 30 kHz?

3. An LM675 has a slew rate of 8V/µs. What is the

power bandwidth for a peak output voltage of 5V?

4. What is the open loop voltage gain of an LF157A

when the input frequency is 1 kHz? 10 kHz? 100 kHz?

(Assume a first order response, that is, 20 dB per

decade rolloff.)

CHAPTER 19|Negative Feedback



1. A VCVS amplifier uses an LM741C with f unity = 1 MHz

and SR = 0.5 V/µs. If ACL = 5, what is the closed loop

bandwidth? The largest undistorted peak output

voltage at f 2(CL)?

2. An ICVS amplifier uses an OP-42E with AOL = 500,000

and f 2(OL) = 20 Hz. What is the closed loop

bandwidth?

3. A VCVS amplifier uses an LM324 with (1 + AOLB) =

2000 and f 2(OL) = 2 Hz. What is the closed loop

bandwidth?

CHAPTER 21|Active Filters

1. A bandpass filter has lower and upper cutoff

frequencies of 445 and 7800 Hz, respectively. What

are the bandwidth, center frequency, and Q? Is this a

wideband or narrowband filter?

2. Identify the following filters as narrowband or

wideband: a) f 1 = 2.3 KHz, f 2 = 4.5 kHz; b) f 1 = 47 kHz

and f 2 = 75 kHz; c) f 1 = 2 Hz and f 2 = 5 Hz; d) f 1 = 80 Hz

and f 2 = 160 Hz

3. If a Butterworth filter contains 10 capacitors, what is

its roll-off rate?

4. A bandpass filter has a center frequency of 50 kHz

and a Q of 20. What are the cutoff frequencies?

5. You are testing a butterworth filter with the

following specifications: n = 10, Ap = 3 dB, and f C = 2

kHz. What is the attenuation at each of the following

frequencies? 4, 8 and 20 kHz?

6. A Chebyshev Sallen-Key unity-gain low-pass filter has

a cutoff frequency of 7.5 kHz. The ripple depth is 12

dB. If n = 2 and R = 25 kΩ, what do C1 and C2 equal?

CHAPTER 23|Oscillators

1. Draw the block diagram of a PLL.

2. A crystal has these values: L = 3 H, CS = 0.05 pF, R =

2kΩ, and Cm = 10 pF. What are the series and parallel

resonant frequencies of the crystal?

3. An Armstrong oscillator has M = 0.1 µH and L = 2µH.

What is the feedback fraction? What is the minimum

voltage gain needed to start the oscillations?

4. A crystal has a thickness of t. If you reduce t by 1

percent, what happens to the frequency?

5. A 555 timer is connected for monostable operation.

IF R = 10 kΩ anc C = 0.022 µF, what is the width of

the output pulse?

6. An astable 555 timer has R1= 10 kΩ, R2 = 2kΩ, and C

= 0.0047 µF. What is the frequency?

CHAPTER 24|Regulated Power Supplies

1. In a buck regulator LT1074, R1 = 2.21 kΩ and R2 = 2.8

kΩ. What is the output voltage?

2. In the buck boost regulator MAX631, R1 = 1kΩ and R2

= 5.79 kΩ, what is the output voltage?

3. The LM7805 can regulate specifications with an

input voltage between 7.5 and 20 V. What is the

maximum efficiency? What is the minimum

efficiency?

4. If a power supply has an output resistance of 1.5 Ω

and the minimum load resistance is 10Ω, it has a

load regulation of ________.

5. Suppose that a power supply has these measured

values:

VLL = 9.2 V for line voltage 105 Vrms

VHL = 11.2 V for line voltage 125 V rms

What is the line regulation?

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