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Question 2(a)

-

Consider the circuit

-

a circuit that switches a

motor on and off for speed/direction control. In this case, the motor being driven expects 12

V

across its terminals in order

to yield peak mechanical output. The motor load is represented in the circuit by the fixed resistor,

RLOAD.

Vdd

Vdd

ni

RGI

VIN

RDI

¼JL

(

)

3.12

2.5

V

Q2

TDSON

5.025 fl

For

W)=230.4rnA/V

2

V

2

=

-

4V

rDsON

12

V

RLOAD

2 fl

RD

1

1

Kfl

RG

1

RG

2

transistors. Assume that

17!N

5

V,

an input level which should correspond to an output state where the motor is

running/operating at maximum mechanical output. Indicate if you think the circuit has been design correctly for its intended

application, briefly explaining why or why not based on your calculations.

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ID,

'D2

VD S,

=

=

Qi Mode

Page s/li

/

201

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Question

2(b)

-

Consider the

partially

complete MOSFET

amplifier circuit shown

below. Ignore r

0

in all calculations.

'daD

Given:

V

DD

=l2V

k'

('=10mA/V2

RD

fl

)

FID

U

V..=2.5V

VOW

(a) Draw in an appropriate

biasing arrangement

in the highlighted space on the

circuit

diagram

;

in order to create a

small-

signal amplifier with

these

parameters:

RIN

100

Kfl

R0ur 4

Kf1

A

0

=

—12.5

V/V

Your biasing arrangement may

consist of

up to

two

resistors

(R

1

and

R

2

).

All resistors used must connect to

the MOSFET

gate with

one

terminal,

but

may

connect to

any

other place in the

circuit with their

second

terminal (including

VDD

and

ground). Given your

circuit,

solve

for

all

unknown

resistor values,

including

RD,. R

5

,

and any

resistors you added.

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/25].

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R

1

=

R2

=

(If used)

R=

RD=

Student Number:

Last Name:

Question 3(a)

-

Consider the BJT amplifier circuit shown below. Include the Early effect

in

your calculations.

Vcc

Vcc

VIN

fl

=

100

VCESAT

=

1.0

V

VA

=50

V

F

—

c

VOLIT

R

1

=

100

Kfl

R

2

=

100 K1

RE

=

5 Kfl

VCC

10V

Find the value of the small-signal parameters

A

0

and

ROUT

for the above amplifier.

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RoUT=

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/251

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(b) You later connect a second amplifier stage ('New Circuit') to the input of the circuit from Part A ('Circuit A'). Your goal in

doing so is to create a two-stage amplifier with the overall properties listed below:

New Circuit

Circuit A

RIN (Total)E

*r

H

ROUT (Total)

RIN (Total)

~! 200

Kf1

R0 (Total)

!~ 32 fl

IAvoI

(Total)

30

Based on standard results, what type of one-transistor

MOSFET

or BJT amplifier would you select for the new circuit and

why? Justify your response in 2-3 sentences.

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