EXPERIMENT 2

Title of the Experiment: Design and simulate positive and negative clippers using diodes with Input signal of 5V peak sine wave at  1kHz and assume suitable reference voltage. Plotting the output wave-forms and transfer curve.

 Aim or Objective : Design and simulate positive and negative clippers using diodes with input signal of 5V peak Sine wave at  1kHz and  by assuming suitable reference voltage.

 Plotting the output wave-forms and transfer curve.

a) Identify and compare series and parallel diode clippers and understand their respective behaviors in signal clipping.

b) Observe and interpret the input and output waveforms, understanding how the clipping level is

determined by the diode orientation and reference voltage

List of components/Equipment's in LT-SPICE:

Theoretical background for the experiment/validation of the experiment:

The process by which the shape of a signal is changed by passing the signal through a network consisting of linear elements is called linear wave shaping. Most commonly used wave shaping circuit is clipper. Clipping circuits are those, which cut off the unwanted portion of the waveform or signal without distorting the remaining part of the signal. There are two types of clippers namely parallel and series. A series clipper is one in which the diode is connected in series with the load and a parallel clipper is one in which the diode is connected in parallel with the load.

Theory

A positive clipper circuit removes the positive half-cycle of an AC signal above a certain threshold level. The diode is forward-biased during positive peaks, limiting the voltage across the load resistor (R4).

In this experiment:

1. V1 is a sinusoidal voltage source with an amplitude of 5V and a frequency of 1kHz.

2. The diode 1N4148 is oriented such that it allows the negative part of the input waveform to pass unaltered while clipping the positive part.

3. R2 (100Ω) and R4 (500Ω) are used to control the current flow and voltage division.

In the above graph the blue line represents the clipped voltage and it is clipped on the positive side so it is called positive clipper.

And the green line represents the line without clipped voltage.

The diagram is simulated for a transient analysis over 5ms. 

Procedure

1. Circuit Setup:

   • Connect the components as per the circuit diagram:

     • Connect a sine wave voltage source with 5V peak and 1kHz frequency.

     • Place a resistor R2​ (100Ω) in series with the voltage source.

     • Connect the diode D1​ (1N4148) in parallel with resistor R4​ (500Ω) as shown.

     • Ensure the diode’s cathode is pointing towards the resistor R4​ for proper clipping behavior.

Simulation:

• Open the simulation tool (e.g., LTspice).

• Run a transient analysis for 5ms (.tran 5ms) to observe the wave-forms

• Observation:

  1. Plot the input waveform (voltage across V1​).

  2. Plot the output waveform across R4​ (voltage after clipping).

  3. Observe the clipping of the positive peaks due to the forward-biased diode.

• Waveforms 

Expected Results

• The input signal’s positive peaks will be clipped, and the output waveform will show only the unaltered negative half-cycles.

• The clipping level will depend on the diode’s forward voltage drop (~0.7V for 1N4148).

Analysis

1. Positive Clipping: The diode conducts during positive peaks and limits the voltage across R4​ to the diode’s forward voltage (0.7V).

2. Negative Cycle: The diode remains reverse-biased, allowing the negative half-cycle to pass without distortion.

Conclusion

• The positive clipper circuit successfully clips the positive half-cycle of the input sinusoidal signal.

• The output waveform confirms that clipping occurs at the diode’s forward voltage level.

Simulation Notes

• Simulation can be performed using tools like LTspice, Multisim, or Proteus.

• Verify the results with theoretical calculations and observe the impact of changing resistance values.

Negative clipper circuit :

Experiment Title: Analysis of a Negative Clipper Circuit

Objective:

To study and analyze the behavior of a negative clipper circuit using a silicon diode and observe its effect on an input sine wave.

Apparatus Required:

1. Software: LTSpice (or equivalent simulation tool).

2. Components:

   • Voltage source (V1) with sine wave: 5Vpeak,1 kHz

   • Resistor: R1=500 Ω

   • Diode: 1N4148

3. Simulation Time: Transient Analysis over 5 ms.

Circuit Diagram:

The following components are used in the circuit:

• V1: Input sine wave of amplitude 5 V and frequency 1 kHz.

• D1: 1N4148 diode to perform negative clipping.

• R1: Load resistor of 500 Ω

The circuit is as follows:

• The diode is placed across the load resistor with its anode connected to ground.

• The input sine wave is applied through the resistor R1.

In the above experiment the blue line represents the clipped voltage and the yellow line represents the unclipped voltage and we can see that the blue line is clipped in the negative side so it is called neagative clipper

 Theory:

A negative clipper circuit removes or clips the negative portion of the input signal. When a diode is forward-biased during the negative cycle of the input, it conducts and clamps the voltage to approximately 0 V (considering the ground connection). The output voltage across the load resistor R1 becomes zero during this time.

For a 1N4148 diode:

• The forward voltage drop Vf​ ≈ 0.7V(silicon diode).

Observations:

• The input waveform is a 5 V sine wave.

• The negative portion of the input voltage is clipped to 0 V because the diode conducts during the negative half-cycle, allowing no voltage across R1.

• The positive portion remains unaffected.

Results:

• The circuit successfully demonstrates negative clipping.

• Output voltage waveform:

  • Positive half-cycle remains as is.

  • Negative half-cycle is clipped near 0 V.

Conclusion:

The negative clipper circuit removes the negative portion of the input signal using a diode. The simulation results verify the clipping effect.

Graph:

1. Green Curve: Input voltage (V1).

2. Blue Curve: Output voltage across R1.

Shunt positive clipper circuit:

Experiment Title: Analysis of a Positive Clipper Circuit using a Diode

Objective:

To study and analyze the behavior of a positive clipper circuit (shunt clipper) using a silicon diode and observe its effect on the positive half-cycle of an input sine wave.

Apparatus Required:

1. Software: LTSpice (or equivalent simulation tool)

2. Components:

   • Voltage source (V1) with sine wave: 10Vpeak,100 Hz;

   • Resistor (R1): 1 kΩ

   • Diode (D1): 1N4148 (silicon diode)

3. Simulation Time: Transient Analysis over 50 ms

Circuit Diagram:

• V1: Sine wave input source with an amplitude of 10V and frequency 100 Hz.

• R1: 1 kΩ in series with the input signal.

• D1: 1N4148 diode, connected in shunt (parallel) with the load and grounded at its cathode.

Connections:

• The positive terminal of the input signal is applied through R1, with the diode connected such that its anode is connected to the node before R1 and cathode to ground.

Theory:

A positive clipper circuit removes or "clips" the positive half of an input signal.

1. During the positive half-cycle of the input signal:

   • The diode becomes forward-biased when the voltage exceeds the forward voltage drop (Vf≈0.7V) of the silicon diode.

   • As a result, the output voltage across R1 gets clipped to approximately 0.7 V (diode drop).

2. During the negative half-cycle:

   • The diode becomes reverse-biased, and no current flows through it.

   • Therefore, the input signal passes unaltered to the output.

Theory:

A negative clipper circuit removes or "clips" the negative half of an input signal.

1. During the negative half-cycle of the input signal:

   • The diode becomes forward-biased when the voltage exceeds the forward voltage drop (Vf≈−0.7V) of the silicon diode.

   • As a result, the output voltage across R1 gets clipped to approximately -0.7 V (diode drop).

2. During the positive half-cycle:

   • The diode becomes reverse-biased, and no current flows through it.

   • Therefore, the input signal passes unaltered to the output.

Observations:

• The input waveform is a 10 V sine wave.

• The negative portion of the waveform is clipped to approximately −0.7Vdue to the forward voltage drop of the diode.

• The positive portion of the waveform remains unchanged.

Results:

• The circuit successfully demonstrates negative clipping of the input signal.

• The negative half-cycle of the sine wave is clipped, while the positive half-cycle is unaffected.

• Conclusion:

• A shunt negative clipper circuit removes the negative half-cycle of the input signal, with the clipped voltage approximately equal to the diode's forward voltage drop (−0.7 V) for a silicon diode.

Graph Interpretation:

1. Blue Curve: Input sine wave (Vin​)

2. Green Curve: Output voltage (Vout​)

The negative half of the waveform is clipped to −0.7V while the positive half remains unaffected.