TÀI LIỆU Filter TA lab

Design the 1st order passive lowpass filter with the cut off frequency of 20 kHz.. Use the Bode plotter to sketch the curve of voltage gain in dB and frequency from 100 Hz to 1 MHz... Fi

Filter Design Lab

Instruments

XBP2

IN OUT

XSC1

Tektronix

1 2 3 4 T G

P

Figure 1

1 Lowpass filter

1.1 Design the 1st order passive lowpass filter with the cut off frequency of 20 kHz

V1

2.8 Vpk 20kHz 0°

R1

7.8kΩ

1nF

XSC1

Tektronix

1 2 3 4 T G

P

V2

Figure 2

Run the simulation and explain the relationship between V1 and V2

Use the Bode plotter to sketch the curve of voltage gain in dB and frequency (from 100 Hz to 1 MHz)

Cuong Ngo

2.8 Vpk 20kHz 0°

R1

7.8kΩ

C1 1nF V2

XBP1

IN OUT

Figure 3

Make sure that the following settings are selected: Magnitude, Vertical (Log, F=0 dB, I= -40 dB), Horizontal (Log, F=1 MHz, I= 100 Hz)

Figure 4

Observe the attenuation at the frequency of about 200 kHz (move the cursor)

Figure 5

Use the Bode plotter to sketch the phase response Note that Bode plotter is in Phase Mode and its vertical setting is linear

Figure 6

1.2 Design the 1st order active lowpass filter with the cut off frequency of 4 kHz, gain of 3

V1

1.4 Vpk 4kHz 0°

R1

3.9kΩ

10nF

V2

U1

741

3

2

4

7

6

5 1

VCC 12V

VEE -12V

R2 10kΩ

R3

22kΩ

XSC1

Tektronix

1 2 3 4 T G

P

Figure 7

Find the gain of this circuit in dB and comment the following result

Figure 8

1.3 Second order lowpass filter (Sallen-Key topolofy)

The task is to design a second order Butterworth lowpass filter with the cut-off frequency of 3 kHz

V1

1.4 Vpk

3kHz

0°

R2

4.9kΩ

10nF

V2

U1

741

3

2

4

7

6

5 1

VCC 12V

VEE -12V

XSC1

Tektronix

1 2 3 4 T G

P R1

2.7kΩ 5%

C2

22nF

Figure 9

Sketch the input and output signal

Use the Bode plotter to verify the amplitude response and to observe the 40 dB/decade roll-off (in the case of 2nd order lowpass filter)

2 Highpass filter

2.1 First order highpass filter: cut-off frequency fc=400 Hz

Verify the circuit in Figure 10

1.4 Vpk

400 Hz 0°

R1 3.9kΩ 5%

C1

100nF V2

XSC1

Tektronix

1 2 3 4 T G

P

Figure 10

Sketch the amplitude and phase response with the help of Figure 11

Figure 11

2.2 First order active highpass filter: fc=400 Hz

1.4 Vpk

400 Hz 0°

R1 3.9kΩ 5%

C1

100nF V2

U1

741

3

2

4

7

6

5 1

VCC 12V

VEE -12V

R2 10kΩ

R3

22kΩ

Figure 12

Compare the difference between the amplitude response of circuit in Figure 11 and of circuit in Figure

12

3 Bandpass filter: passband from 400 Hz to 4 kHz

V1

1.4 Vpk

400 Hz

0°

R1 3.9kΩ 5%

C1

100nF V2

U1

741

3

2

4

7

6

5 1

VCC 12V

VEE -12V R2

10kΩ

R3 22kΩ

R4 3.9kΩ

10nF

V2

U2

741

3

2

4

7

6

5 1

VCC 12V

VEE -12V R5 10kΩ

R6 22kΩ XBP1

IN OUT

Comment on amplitude response

Figure 14