What is the use of positive clipper

Clipper circuits

Clipper circuits

Chapter 3 - Diodes and Rectifiers

A circuit that removes the top of a waveform is known as a clipper. A negative clipper is shown in the figure below. This schematic diagram was created with the Xcircuit schematic capture program. Xcircuit created the SPICE netlist Figurebelow, except for the second and penultimate pair of lines, which were inserted with a text editor.

* SPICE 03437.eps * AK Model name D1 0 2 Diode R1 2 1 1.0k V1 1 0 SIN (0 5 1k) .Modeldiode d .tran .05m 3m .end

Clipper: cuts negative tip at -0.7 V.

During the positive half cycle of the 5 V peak input, the diode is reverse biased. The diode does not conduct. It's like the diode isn't there. The positive half cycle is unchanged at output V (2) in FIG. 8. Since the positive peaks of the output signal are actually superimposing the input sine wave V (1), the input has been moved up on the graph for clarity. In Nutmeg, the SPICE display module, this is done by the command "plot v (1) +1)".

V (1) +1 is actually V (1), a 10 Vptp sine wave offset by 1 V for clarity of the display. The output of V (2) is limited to -0.7V by diode D1.

During the negative half cycle of the sine input of Figure Above, the diode is forward biased, i.e. conductive. The negative half-wave of the sine wave is short-circuited. The negative half cycle of V (2) would be cut off at 0V for an ideal diode. The waveform is limited due to the forward voltage drop of the silicon diode at -0.7V. The Spice model is set to 0.7 V by default, unless the parameters specify otherwise in the model instruction. Germanium or Schottky diodes cut off at lower voltages.

Closer inspection of the negatively clipped peak (image above) shows that it follows the input for a short period of time as the sine wave moves in the -0.7V direction. Clipping is only effective after the input sine wave exceeds -0.7V for most of it but non-conductive for the entire half cycle.

The addition of an anti-parallel diode to the existing diode in FIG. Above results in the symmetrical limiter in FIG. 8.

* SPICE 03438.eps D1 0 2 Diode D2 2 0 Diode R1 2 1 1.0k V1 1 0 SIN (0 5 1k) .Modeldiode d .tran 0.05m 3m .End

Symmetrical clipper: anti-parallel diodes cut off both positive and negative peaks so that an output of ± 0.7V is maintained.

Diode D1 cuts off the negative spike at -0.7V as before. The additional diode D2 conducts the forward diode drop for positive half waves of the sine wave when it exceeds 0.7 V. The rest of the voltage drops across the series resistor. Thus, both peaks of the input sine wave are cut off in FIG. The netlist is in the figure above

Diode D1 cuts at -0.7V while conducting during negative peaks. D2 conducts for positive peaks, clipping at 0.7 V.

The most general form of the diode limiter is shown in FIG. For an ideal diode, clipping occurs at the level of the limit voltages V1 and V2. However, the voltage sources have been adjusted to account for the 0.7 V forward drop of the real silicon diodes. D1 sticks at 1.3V + 0.7V = 2.0V when the diode begins to conduct. D2 sticks at -2.3 V -0.7 V = -3.0 V when D2 conducts.

* SPICE 03439.eps V1 3 0 1.3 V2 4 0 -2.3 D1 2 3 Diode D2 4 2 Diode R1 2 1 1.0k V3 1 0 SIN (0 5 1k) .Modeldiode d .tran 0.05m 3m .end

D1 cuts the input sine wave at 2V. D2 clips at -3V.

The clipper in Figure Above doesn't have to cut off both layers. To separate one level with a diode and a voltage source, remove the other diode and source.

The netlist is in the figure above. The waveforms in the figure below show the clipping of v (1) at the output v (2).

D1 intersects the sine wave at 2V. D2 clips at -3V.

There is also a Zener diode limiter circuit in the "Zener Diode" section. A Zener diode replaces both the diode and the DC voltage source.

One practical use of a hair clipper is to prevent an amplified voice signal from overdriving a radio transmitter in the figure. When overdriven, the transmitter generates disruptive radio signals that cause interference with other stations. The clipper is a protective measure.

Clipper prevents radio transmitters from being overdriven by speech peaks.

A sine wave can be squared by overdriving a clipper. Another application of Clipper is protecting exposed inputs of integrated circuits. The input of the IC is connected to a pair of diodes as at node "2" of Figure Above. The voltage sources are replaced by the power supply rails of the IC. For example, CMOS ICs use 0V and +5V. Analog amplifiers can use ± 12V for the V1 and V2 sources.

  • A resistor and a diode, which are controlled by an AC voltage source, cut off the signal observed at the diode.
  • A pair of anti-parallel Si diodes cut symmetrically at ± 0.7V
  • The grounded end of one or more clipper diodes can be disconnected and connected to a DC voltage to clamp at any level.
  • A clipper can act as a protective measure and prevent a signal from exceeding the clip limits.