Slide 1EE100 Summer 2008 Bharathwaj Muthuswamy

EE100Su08 Lecture #13 (July 25th 2008)• Outline

– MultiSim licenses: postponed to Monday, July 28th 2008• Apparently our license number is not working!• Thanks for coming to lecture today!

– HW #2: regrade deadline: Monday, 07/28, 5:00 pm PST.– Midterm #1 regrades: I will finish em by office hours today.– QUESTIONS?– Strain Gauge and Project: Lab Lecture

• WARNING: BE REALLY CAREFUL AROUND THE STRAIN GAUGE SINCE THE APPARATUS “STICKS OUT” OF THE TABLE!

– Frequency Response and Bode plots– Nonlinear circuits

• Reading– Chapter 9 from your book (skip 9.10, 9.11 (duh)), Appendix E*

(skip second-order resonance bode plots)– Chapter 1 from your reader (skip second-order resonance bode

plots)

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Slide 7EE100 Summer 2008 Bharathwaj Muthuswamy

Example Circuit

)1()/1

)/1(

22 CRj

A

CjR

jwCA

IN

OUT

V

V

IN

OUTnctionTransferFuV

V

+AVT

R2

R1

+

VT

+

VOUTCVIN

+

cR

c

IN

OUT

ZZ

AZ

V

V

A = 100

R1 = 100,000 Ohms

R2 = 1000 Ohms

C = 10 uF

Slide 8EE100 Summer 2008 Bharathwaj Muthuswamy

Example Circuit

+AVT

R2

R1

+

VT

+

VOUTCVIN

+

A = 100

R1 = 100,000 Ohms

R2 = 1000 Ohms

C = 10 uF

Slide 9EE100 Summer 2008 Bharathwaj Muthuswamy

Example Circuit

+AVT

R2

R1

+

VT

+

VOUTCVIN

+

A = 100

R1 = 100,000 Ohms

R2 = 1000 Ohms

C = 10 uF

Slide 10EE100 Summer 2008 Bharathwaj Muthuswamy

Break Point Values

• When dealing with resonant circuits it is convenient to refer to the frequency difference between points at which the power from the circuit is half that at the peak of resonance.

• Such frequencies are known as “half-power frequencies”, and the power output there referred to the peak power (at the resonant frequency) is

• 10log10(Phalf-power/Presonance) = 10log10(1/2) = -3 dB.

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Example: Circuit in Slide #2 Magnitude

)1( 2CRj

A

IN

OUT

V

V

1

10

100

1000

0.110 100 10001 Radian

Frequency

A = 100

R2 = 1000 Ohms

C = 10 uF

wp = 1/(R2C) = 100A

Mag

nitu

de

Actual value = 2

100

|1|

100

j

Slide 12EE100 Summer 2008 Bharathwaj Muthuswamy

Bode Plot: Label as dB

0

20

40

60

-2010 100 10001 Radian

Frequency

)1( 2CRj

A

IN

OUT

V

V

A = 100

R2 = 1000 Ohms

C = 100 uF

wp = 1/(R2C) = 100A

Mag

nitu

de in

dB

Note: Magnitude in dB = 20 log10(VOUT/VIN)