precision full wave rectifier

EXPT.1 - PRECISION RECTIFIER

AIM: Design and test the working of Full Wave Precision Rectifier using op-amp

THEORY: Precision Rectifier name itself suggests that it rectifies even lower input voltages i.e. voltages less than 0.7v (diode drop). A rectifier is a device, which converts AC voltage to DC voltage. Precision rectifier converts AC to pulsating DC. Normal rectifiers using transformers cannot rectify voltages below 0.7v, so we go for precision rectifiers. In this circuit the diodes are placed in such a way that one diode is forward biased in the positive half cycle and the other in the negative half cycle. Consider the circuit diagram shown below. Here in the positive half cycle D1 is forward biased and D2 is reverse biased. The simplified circuit will act as two inverted amplifiers connected in series. Hence the total gain will be the product of individual gains. During the negative half cycle, D1 is reverse biased and D2 is forward biased. Hence the simplified circuit is an inverting amplifier connected in series with a non-inverting amplifiers. Hence the output will be inverted and a DC output (unidirectional) is obtained .The precision rectifier we are using is a full wave rectifier.

PROCEDURE:

1. Rig up the circuit as shown in the circuit diagram.

2. Give an input of 2V peak to peak (sine wave).

3. Check and verify the designed values.

4. Design the same circuit for a different set of values.

RESULT:

 

Schmitt trigger

EXPERIMENT NO. 3 DESIGN AND TEST A SCHMITT TRIGGER CIRCUIT FOR THE GIVEN VALUES OF UTP AND LTP

 AIM: Design a square wave generator for a given UTP and LTP

THEORY: Schmitt Trigger is also known as Regenerative Comparator. This is a square wave generator which generate a square based on the positive feedback applied. As shown in the fig. below, the feedback voltage is Va. The input voltage is applied to the inverting terminal and the feedback voltage is applied to the non-inverting terminal. In this circuit the op-amp acts as a comparator. It compares the potentials at two input terminals. Here the output shifts between + Vsat and –Vsat. When the input voltage is greater than Va, the output shifts to – Vsat and when the input voltage is less than Va, the output shifts to + Vsat. Such a comparator circuit exhibits a curve known as Hysterisis curve which is a plot of Vin vs V0. The input voltage at which the output changes from + Vsat to – Vsat is called Upper Threshold Point (UTP) and the input voltage at which the output shifts from – Vsat to + Vsat is called Lower Threshold Point (LTP). The feedback voltage Va depends on the output voltage as well as the reference voltage. A Zero Cross Detector is also a comparator where op-amp compares the input

PROCEDURE:

1. Rig up the connections as shown in the circuit diagram.

2. Give a sinusoidal input of 10V peak to peak and 1 kHz from a signal generator.

3. Check the output at pin no. 6 (square wave).

4. Coincide the point where the output shifts from + Vsat to – Vsat with any point on the input wave.

5. Measure the input voltage at this point. This voltage is UTP.

6. Coincide the point where the output shifts from – Vsat to + Vsat with any point on the input wave.

7. Measure the input voltage at this point. This voltage is LTP.

8. Another method of measuring UTP and LTP is using the Hysterisis Curve.

9. To plot the hysterisis curve give channel 1 of CRO to the output and channel 2 of CRO to the input.

10. Press the XY knob. Adjust the grounds of both the knobs.

11. Measure UTP and LTP as shown in the fig. and check whether it matches with the designed value.

RESULT:.

High pass filter

EXPERIMENT N0. 1(B) SECOND ORDER ACTIVE HIGH PASS FILTER

AIM: To obtain the frequency response of an active high pass filter for the desired cut off frequency

PROCEDURE:

1. Before wiring the circuit, check all the components.

2. Design the filter for a gain of 1.586  and make the connections as shown in the circuit diagram.

3. Set the signal generator amplitude to 2v  peak to peak and observe the input voltage and output voltage on the CRO

4. By varying the frequency of input from Hz range to KHz range, note the frequency and the corresponding output voltage across pin 6 of the op amp with respect to the gnd.

5. The output voltage (VO) remains constant at lower frequency range.

6. Tabulate the readings in the tabular column.

7. Plot the graph with ‘f ‘on X-axis and gain in dB on Y axis.

RESULT:

Low pass filter

EXPERIMENT N0. 2(A) SECOND ORDER ACTIVE LOW PASS FILTER

AIM: To obtain the frequency response of an active low pass filter for the desired cut off frequency.

PROCEDURE:

1. Before wiring the circuit, check all the components.

2. Design the filter for a gain of 1.586 and make the connections as shown in the circuit diagram.

3. Set the signal generator amplitude to 2v  peak to peak and observe the input voltage and output voltage on the CRO

4. By varying the frequency of input from Hz range to KHz range, note the frequency and the corresponding output voltage across pin 6 of the op amp with respect to the gnd.

5. The output voltage (VO) remains constant at lower frequency range.

6. Tabulate the readings in the tabular column.

7. Plot the graph with ‘f ‘on X-axis and gain in dB on Y axis.

RESULT:

Precision half wave rectifier

EXPT.1 - PRECISION RECTIFIERS

AIM: Design and test the working of half Wave Precision Rectifier using op-amp

PROCEDURE:

1. Rig up the circuit as shown in the circuit diagram.

2. Give an input of 2V peak to peak (sine wave).

3. Check and verify the designed values.

4. Design the same circuit for a different set of values.

RESULT: