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LINEAR WAVE SHAPING

Aim : Design a RC LPF and HPF at various time constants and verify the responses for Square wave input (choose C = 0.1f, Vi = 4 VP-P, f = 10 K Hz).

Apparatus : 1. CRO2. Signal Generator3. Bread board4. Capacitor (0.1f)5. Resistors (100, 1K, 10 K)6. Connecting wires.

Circuit Diagram:

HPF :

Design / Calculations:

a) RC = TGiven T = 1/10KHz = 0.1 mSec

R = 0.1x 10-3 / 0.1f = 1 Kohms

V1 = V / (1 + e-T/2RC) = 2.49 V

= (2.49 – 1.51)/2 = 49%)

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T1 = T2 = T/2

b) RC >> T Choose RC = 10T = 1 mSec

R =

The O/P waveform will be identical to I/P

T1 = T2 = T/2

c) RC << T RC = 0.1 T

R =

LPF:

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a) RC = T

C = 0.1f, R = 1K

V1 = -0.49 V

b) RC >> T

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R = 10 K, C = 0.1 f

V1= 0.05v

c) RC << TR = 100,

C = 0.1 f

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Note:

Low Pass Filter allows the DC component of I/P signal and High Pass Filter block the DC component of I/P Signal.

Procedure:

1. Connect the circuit as shown in figure (LPF / HPF)2. Apply the Square wave input to this circuit (Vi = 4 VP-P, f = 10KHz)3. Observe the output waveform for (a) RC = T, (b) RC>>T, (c) RC>>T4. Verify the values with theoretical calculations

Precautions:Use two CRO probes and observe I/P & O/P waveforms simultaneously by

putting CRO on DC modes.

Result:LPF and HPF are designed at various time constants and the responses for

square wave input is observed & hence plotted.

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Questions :

1. When HP-RC circuit is used as Differentiator?

2. Draw the responses of HPF to step, pulse, ramp inputs?

3. Draw the responses of LPF to step, pulse, ramp inputs?

4. Define % tilt and rise time?

5. When LP-RC circuit is used as integrator?

6. Why noise immunity is more in integrator than differentiator?

7. Why HPF blocks the DC signal?

8. Define 1db?

9. What is meant by linear wave shaping?

10. Write the formula for rise time tr?

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