Parallel Clippers

1. Parallel Clippers Prepared By:Eng.Maira Naz Dated:01-08-2011

3. Applications of diode

4. Applications of Diodes • Clippers. • Clampers. • Peak Detectors. • Voltage Multipliers. • Simple Logic Gates. • DC Power Supply. • Filtering Circuits.

5. Clippers

6. Clippers • Clippers, limiters or clipping circuits make use of non-linear properties of diode, that is the diode conduct the current in forward direction and does not conduct in reverse direction.

7. Clippers Basic operating Principle: • These circuits are primarily are wave shaping circuits. • They clip or remove certain portion of ac voltage applied to the input of circuit.

8. Clippers Applications of Clippers: • They need to clip the voltage above or below a certain pre-determined voltage level arises in the television, digital computers, radar, and many other electronic circuits.

9. Clippers Components of clipping circuits: • The clipping circuits used in electronics are not necessarily composed of simple diodes and resistors, they employ more advance components to do so. • The basic principle however remains the same.

10. Clippers Steps to analyze clipper circuits. • Replace the diode by one of its equivalent models. • Identify ON and OFF states of diodes and clipping levels of Vin. • Derive the equation for transfer characteristics of the circuit. • Plot the transfer characteristics and input-output waveforms of the circuit.

11. Clippers

12. Clippers Further Classification:

13. Clippers Further Classification (Cont..) :

14. Parallel Clippers

15. Parallel Clippers Parallel Clippers: • The name parallel clipper stems from he fact that the diode is in parallel with load resistance. Unbiased Parallel Clipper: • In parallel unbiased clipper, there ia no battery connected in series with diode.

16. Unbiased parallel clippers

17. Parallel Clippers Unbiased Parallel Clipper: Fig (a) Unbiased parallel clipper

18. Parallel Clippers Unbiased Parallel Clipper (Cont..): • Fig (a) shows, unbiased parallel clipper in which diode is connected in parallel with load resistance.

19. Parallel Clippers Unbiased Parallel Clipper (Cont..): Fig (b) Input voltage waveform

20. Parallel Clippers Unbiased Parallel Clipper (Cont..): • Fig (b) shows the input voltage waveform that is going to apply at the input of the circuit shown in fig (a). • Mathematically it is represented by the following equation. Vin=VmaxSinωt

21. Parallel Clippers Observation for the analysis of clipping circuit: • Vmax should be greater than 0.7V built in potential of the silicon diode or 0.2 for germanium. • RL should be greater than Rin. RL>>Rin Or RL~10Rin • So, that the voltage drop across Rin can be neglected.

22. Analysis of unbiased parallel clippers with positive clipping(Ideal diode)

23. Parallel Clippers Unbiased Parallel Clipper (Cont..): Ideal Diode: • First, we should replace the given diode with an ideal one i.e., we should consider the ideal model of diode.

24. Parallel Clippers Unbiased Parallel Clipper (Cont..): Action during the positive half cycle:

25. Parallel Clippers Unbiased Parallel Clipper (Cont..): Action during the positive half cycle: • During the positive half cycle of the input voltage, the diode becomes forward biased and remains forward biased for entire half cycle of the input.

26. Parallel Clippers Unbiased Parallel Clipper (Cont..): Action during the positive half cycle: • As ideal diode acts as short circuit when forward biased, the current I flows entirely through diode. • The drop across short circuit diode is zero.

27. Parallel Clippers Unbiased Parallel Clipper (Cont..): Action during the positive half cycle: • As RL is in parallel with diode no current flows through it and output voltage Vo=0V. • This condition remains for entire positive half cycle of the input. • Thus positive half cycle gets clipped off.

28. Parallel Clippers Unbiased Parallel Clipper (Cont..): Action during the negative half cycle:

29. Parallel Clippers Unbiased Parallel Clipper (Cont..): Action during the negative half cycle: • During the negative half cycle, the diode is reverse biased and acts as open circuit. • The entire current flows through RL. • So, output voltage can be found by using VDR. • Vo = Vin RL/(Rin+RL) Where Vin= - Vm. • Since, RL>>Rin. • So, Rin can be neglected in comparison to RL.

30. Parallel Clippers Unbiased Parallel Clipper (Cont..): Action during the negative half cycle: • So, we can also write Vo=K Vin. Where K=RL/ Rin+RL. • So, during negative half cycle , proportionate negative half cycle is available at the output. • There exits a straight line relationship between input and output voltage.

31. Parallel Clippers Unbiased Parallel Clipper (Cont..): Output waveform:

32. Parallel Clippers Unbiased Parallel Clipper (Cont..): Transfer characteristics: • The graph of output variable against the input variable of the circuit is called as the transfer characteristics of the circuit.

33. Parallel Clippers Unbiased Parallel Clipper (Cont..): Equation for transfer characteristics: • Transfer Characteristic equation for the circuit shown in fig (a) Vo=0V …..for Vi ≥ 0V Vo=Vin RL/Rin+RL, …..for Vi < 0V

34. Parallel Clippers Unbiased Parallel Clipper (Cont..): Positive parallel Clippers: • Circuit shown in fig (a) is called as parallel clipper with positive clipping because it clips the positive half cycle of input voltage.

35. Analysis of unbiased parallel clippers with positive clipping(Practical diode)

36. Parallel Clippers Unbiased Parallel Clipper (Cont..): Practical silicon diode: • Now, we consider that the diode is not an ideal one and we must consider its 2nd model i.e., a Vd is connected in series with the diode.

37. Parallel Clippers Unbiased Parallel Clipper (Cont..): Practical silicon diode:

38. Parallel Clippers Unbiased Parallel Clipper (Cont..): Practical silicon diode: Action during the positive half cycle

39. Parallel Clippers Unbiased Parallel Clipper (Cont..): Practical silicon diode: Action during negative half cycle

40. Parallel Clippers Unbiased Parallel Clipper (Cont..): Practical silicon diode: Input and output waveforms

41. Parallel Clippers Unbiased Parallel Clipper (Cont..): Practical silicon diode: • Mathematically, it can be expressed as Vo=Vd …..for Vi ≥ Vd Vo=Vin RL/Rin+RL=Vin …..for Vi < Vd

42. Biased parallel clipper

43. Parallel Clippers Biased Parallel Clipper: • In parallel unbiased clipper, there is a battery connected in series with diode

44. Parallel Clippers Analysis of biased parallel clipper: Ideal Diode:

45. Parallel Clippers Analysis of biased parallel clipper: Ideal Diode: • In case of ideal diode, Vd=0V and VBB is connected in series with diode as it is biased parallel clipper. • Now, the battery voltage will appear at one side of diode and input voltage will appear across the other side of diode.

46. Parallel Clippers Analysis of biased parallel clipper: Ideal Diode: • Diode will be the forward biased during the time interval whenever the Vin is greater than VBB. • Diode will be the reverse biased during the time interval whenever Vin is less than VBB.

47. Parallel Clippers Analysis of biased parallel clipper: Ideal Diode: During positive half cycle

48. Parallel Clippers Analysis of biased parallel clipper: Ideal Diode: Output waveform during negative half cycle

49. Parallel Clippers Analysis of biased parallel clipper: Ideal Diode: During the negative half cycle

50. Parallel Clippers Analysis of biased parallel clipper: Ideal Diode: Output waveform during negative half cycle