Biased Double Limiter

  Aim

  To design and simulate a Biased Double Limiter circuit.

  Components

Limiter is a wave shaping circuit used to limit ac voltage to predetermined level. Limiters can transform a sine wave into rectangular wave, can limit either the –ve or +ve alternation or both alternations of an ac voltage. The diode limiters are also known as clippers. Limiters may be classified as Series limiter and Parallel limiter depending on whether the output is taken from the load resistor in series with the diode or in parallel with it.

Circuit Operation: As shown in the above circuit diagram two biased diode limiters are connected in parallel such that the circuit acts as a partial limiter of both the +ve and –ve alternations. During the +ve half cycle of the input voltage D1 remains in the reverse biased state. D2 also remains in the reverse biased state until the input voltage reaches the bias voltage V_aa Thus the output voltage follows the input until D2 is forward biased. Thereafter the output remains constant  at V_aa.

During the –ve half cycle of the input voltage D2 remains in the reverse biased state. D1 also remains in the reverse biased state until the input voltage becomes more -ve than the bias voltage V_kk. Thus the output voltage follows the input until D1 is forward biased. Thereafter the output  remains constant at V_kk.

The output waveform will be a sine wave clipped at >_aa in the + ve half cycle and at V_kk in the – ve half in the – ve half cycle.

Thus the diode limiter modifies the input waveform by limiting part of that waveform thereby changing the shape of the input waveform whose extremities has been squared off.

EDWinXP-> Schematic Editor: The circuit diagram is drawn by loading components from the library. Wiring and proper net assignment has been made. The values are assigned for relevant components.

EDWinXP-> Mixed Mode Simulator: The circuit is preprocessed. The test points and waveform markers are placed at input and output. The Transient Analysis parameters have been set. The Transient Analysis is executed and output waveform is observed in the Waveform Viewer.

Result
   The output waveform may be observed in the waveform viewer.