Hello friends, I hope you are doing great. In today’s tutorial, we will have a look at Diode Limiters Circuits. In some circuits, the ac signal is used at some certain level to achieve that level AC input signal is limited at certain values. Circuit used to limit signal at specified value is known as diode limiter. In these circuits, a diode is connected in parallel combination with the input signal.
In some circuits, only one half of the wave is to be limit so one diode is connected with the input AC source. But if a complete signal or both half of sine waveform is to be limit than two diodes are used. In today’s post, we will have a detailed look at its working, circuit arrangements, applications, and some related parameter. So let’s get started with the Diode Limiters Circuits.
Diode Limiters Circuits
- Diode limiters are also known as clipper circuits that used to clip some portion of the signal.
- In the below figure, you can see a diode is connected in an input ac signal as the positive portion of input signal comes across the diode it becomes in forward biased condition.
- In the above circuit, you can see that this positive signal is limited to +0.7 volts as it set to that value.
- When the input signal goes towards a negative signal diode is now in reverse biased condition and operates as an open circuit.
- The output voltage of this circuitry can be calculated by using the voltage divider rule.
Vout = (RL/R1 + RL) Vin
- If the value of resistor R2 is less than the RL then the output voltage will be equal to an output voltage.
Vout =Vin
- If we vary the direction of the diode as shown in the figure the negative portion of input signal will be limit.
- In this state, a diode is forward biased during a negative cycle of a signal and -0.7 volts will be drop across the diode.
- When the voltage value is larger than the -o.7 volts and a diode is not in a forward-biased condition voltage value across the load resistor is equal to the input supply.
Biased Limiters
- In some conditions, we required voltage above the 0.7 volts or -0.7 volts in these case biased limiter circuits are used.
- The limited voltage can be adjusted by using a bias voltage. This VBIAS is connected in series with the diode as shown in below figure.
- The voltage across should be equal to the VBIAS + 0.7 before it operates in forward bias.
- The VBIAS are voltage that will fulfill our requirement after adding in 0.7 volts.
- After conducting diode all voltage at the input of diode will limit to the VBIAS + 0.7 and the value of voltage above this voltage will be clipped off or limited.
- If we require to limit the negative portion of the input signal then the connection arrangements of diode and battery should be according to given below figure.
- In this case, the voltage at point ‘A’ will be should go below to the -VBIAS – 0.7 to make diode forward biased and limit the signal.
- If you change the direction of the diode than a positive limiter will provide an improvement in its function and will limit the input signal to level as shown in the below figure.
- Like the positive limiter negative limiter can also be modified and limit the input voltage below -VBIAS + 0.7 V shown in the below figure.
Voltage-Divider Bias
- Above we discuss the voltage source as biased voltage now we replace it with the voltage divider circuit of resistances and provide voltage it through dc supply.
- The value of voltage divider formula decides this resistances biased voltage.
VBIAS = (R3/R2 + R3) VSUPPLY
- In the below figure, there are positive limiters, negative limiters, and variable positive limiter circuits are shown.
Diode Limiter Applications
- These are some applications of diode limiters.
- These circuits are used in the production of waveform and design their physical arrangments.
- It provides protection to any circuitry from spikes.
- It also restores the amplitude of any waveform.
- It used to limit value of voltage.
- It also used in TVs.
- The transmitters of frequency modulation also consist of diode limiter or clipper circuits.
So friends that is a detailed post about diode limiter I have mentioned each and every parameter related to diode limiter. If you have any further question ask in comments. Thanks for reading. See you in the next interesting tutorial. Have a good day.
