BAB 16. EFEK FREKUENSI

(Tugas Elektronika Lanjut)

Di susun oleh :

Kelompok 1

Nama NPM

1. Andri Abadi 1215031010

2. Bella Nurbaitty S 1215031016

3. Desi Purnamasari 1215031019

4. Novitiyono Wisnu H 1215031054

5. Risdawati Hutabarat 1215031064

JURUSAN TEKNIK ELEKTRO

FAKULTAS TEKNIK

UNIVERSITAS LAMPUNG

2014

EXAMPLE 16-14

Draw the ideal Bode Plot for the lag circuit of Fig 16-18a

SOLUTION :

Figure 16-18 lag circuit its Bode Plot

We can calculate the cutoff frequency:

f2 = 1

2𝜋(5𝑘𝛺)(100 𝑝𝐹)= 318 kHz

Figure 16-18b shows the ideal Bode plot.

The voltage gain is 0 Db at low

frequencies. The Frequency responses

breaks at 318 kHz and then rolls off at a

rate of 20 Db/decade.

This is result of Bode Plot using Multisim Software.

V1

220 Vpk

1000 Hz

0

R1

5kΩ

C1

100pF

XBP1

IN OUT

EXAMPLE 16-19

Using the circuit values shown in Fig-28a, calculate the low-cutoff frequency for each

coupling and bypass capacitor. Compare the results to a measurement using a bode plot.

(use 150 for the dc and ac beta values)

SOLUTION :

In figure 16-28a, we will analyze each coupling capacitor and each bypass capacitor

separately. When analyzing each capacitor, treat the other two capacitors as ac shorts.

From the past dc calculating of this circuit r’e= 22.7 𝛺. The Thevenin resistance facing

the input coupling capacitor is :

R =RG = (β)(r’e)= (150)( 22.7 𝛺) = 3,41 𝑘𝛺

Thefore,

R= 600 𝛺 + (10 𝑘𝛺 || 2,2 𝑘𝛺 || 3,41 𝑘𝛺)

R= 600 𝑘𝛺 + 1,18 𝑘𝛺 = 1,78 𝑘𝛺

Figure 16.28a

CE amplifier using

MultiSim

Figure 18.28b Result a measurement using bode plot by MultiSim

R1

600Ω

C1

470nF

R2

10kΩ

Q1

2N3904

R3

2.2kΩ

R4

3.6kΩ

R5

1000Ω

C2

10µF

C3

2.2µF

R6

10kΩ

10VVCC

V1

1mVpk

1kHz

0

XBP1

IN OUT

EXAMPLE 16.20

Using the circuit values shown in fig 16-28a, calculate the high-frequency cutoff values

for the base bypass circuit and the collector bypass circuit. Use 150 for the beta and

10pF for the stray output capacitance. Compare he results to a bode plot using

simulation software.

SOLUTION :

First determine the values of transistor input and output capacitance 1,8 V and

Vc=6,04V. This results in a collector to base reverse voltage of approximately 4,2 V.

The value of C’e at this reverse voltage is 2,1 pF.

Results of Bode plot using Multisim Software

VDD

9V

R12MΩ

R2150Ω

Q1

2N7000

C1

10µF

R310kΩ

R41MΩ

R5

600Ω

C3

0.1µF

Vin

50mVrms

0 Hz

0°

XBP1

IN OUT

EXAMPLE 16-21

Using the circuit shown in fig 16-32, determine the input-coupling circuit and output-coupling circuit low frequency cutoff points. Compare the calculated values to a bode

plot using multisim. SOLUTION :

The Thevenin resistance facing the input-coupling capacitor is :

R= 600 Ω + 200 M Ω|| 1 M Ω = 667 k Ω And the input-coupling cutoff frequency is :

f1 = 1

2𝜋(667𝑘𝛺)(0.1 𝜇𝐹)= 2.39 Hz

Next, the Thevenin resistance facing the output coupling capacitor is found by :

R= 150 Ω + 1 kΩ = 1.15 kΩ

And the output coupling cutoff frequency is :

f1 = 1

2𝜋(130𝛺)(10 𝜇𝐹)= 13.8 Hz

Thefore, the dominant low-frequency cutoff value is 13.8 Hz. The midpoint voltage

gain of this circuit is 22.2 dB. The Bode plot in fig-16-32b shows a 3 Db loss at

approximately 14 Hz. This is very close to the calculated value.

Results of Bode plot using Multisim Software

VDD

9V

R12MΩ

R2150Ω

Q1

2N7000

C1

10µF

R310kΩ

R41MΩ

R5

600Ω

C3

0.1µF

Vin

50mVrms

0 Hz

0°

XBP1

IN OUT

EXAMPLE 16-22

In the MOSFET amplifier circuit of fig 16-32, the 2N700 has these capacitances given

on a data sheets.

Ciss = 60 pF

Coss = 25 pF

Crss = 5.0 pF

If gm = 97 mS, What are the high frequency cutoff values for the gate and drain

circuits? Compare the calculations to a bode plot.

SOLUTION :

The high frequency cutoof frequency measures using multisim is approximately 638

kHz. This somewhat inaccurate result demonsreates the difficulty of choosing the

correct internal capacitance values of the device, which are critical to the calculations.

Results of Bode plot using Multisim Software

VDD

9V

R12MΩ

R2150Ω

Q1

2N7000

C1

10µF

R310kΩ

R41MΩ

R5

600Ω

C3

0.1µF

Vin

50mVrms

0 Hz

0°

XBP1

IN OUT

PROBLEM 16.23

Draw the ideal bodeplot for the lag circuit of fig 16-36a

Results of ideal Bode plot using Multisim Software

PROBLEM 16.24

Draw the ideal bodeplot for the lag circuit of fig 16-36b

Results of ideal Bode plot using Multisim Software