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AB88 Diode Clippers

Operating Manual Ver.1.1

An ISO 9001 : 2000 company

94-101, Electronic Complex Pardesipura, Indore- 452010, India Tel : 91-731- 2570301/02, 4211100 Fax: 91- 731- 2555643 e mail : [email protected] Website : www.scientech.bz Toll free : 1800-103-5050

mailto:[email protected]

http://www.scientech.bz

AB88

Scientech Technologies Pvt. Ltd. 2

AB88


RoHS Compliance

Scientech Products are RoHS Complied. RoHS Directive concerns with the restrictive use of Hazardous substances (Pb, Cd, Cr, Hg, Br compounds) in electric and electronic equipments. Scientech products are “Lead Free” and “Environment Friendly”. It is mandatory that service engineers use lead free solder wire and use the soldering irons upto (25 W) that reach a temperature of 450°C at the tip as the melting temperature of the unleaded solder is higher than the leaded solder.

Diode Clippers AB88

Table of Contents

1. Introduction 4

2. Theory 6 3. Experiments

• Experiment 1 11 Study of Parallel positive and negative clipper

• Experiment 2 13 Study of series positive and series negative clipper

• Experiment 3 15 Study of combination clipper

4. Warranty 16 5. List of Accessories 16

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Introduction AB88 is a compact, ready to use Diode clippers experiment board. This is useful for students to understand basics of diodes and clipping circuits. It can be used with Scientech Analog Lab ST2612 which has built in DC power supply, AC power supply, function generator, modulation generator, continuity tester, toggle switches, and potentiometer.

List of Boards : Model Name AB01 Diode characteristics (Si, Zener, LED) AB02 Transistor characteristics (CB NPN) AB03 Transistor characteristics (CB PNP) AB04 Transistor characteristics (CE NPN) AB05 Transistor characteristics (CE PNP) AB06 Transistor characteristics (CC NPN) AB07 Transistor characteristics (CC PNP) AB08 FET characteristics AB09 Rectifier Circuits AB10 Wheatstone Bridge AB11 Maxwell’s Bridge AB12 De Sauty’s Bridge AB13 Schering Bridge AB15 Common Emitter Amplifier AB14 Darlington Pair AB16 Common Collector Amplifier AB17 Common Base Amplifier AB18 Cascode Amplifier AB19 RC-Coupled Amplifier AB20 Direct Coupled Amplifier AB21 Class A Amplifier AB22 Class B Amplifier (push pull emitter follower) AB23 Class C Tuned Amplifier AB25 Phase Locked Loop (FM Demodulator & Frequency Divider /

Multiplier) AB28 Multivibrator ( Mono stable / Astable) AB29 F-V and V-F Converter AB30 V-I and I-V Converter AB31 Zener Voltage Regulator AB32 Transistor Series Voltage Regulator AB33 Transistor Shunt Voltage Regulator AB35 DC Ammeter AB39 Instrumentation Amplifier AB41 Differential Amplifier (Transistorized) AB42 Operational Amplifier (Inverting / Non-inverting / Differentiator) AB43 Operational Amplifier (Adder/Scalar)

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AB44 Operational Amplifier (Integrator/ Differentiator) AB45 Schmitt Trigger and Comparator AB49 K Derived Filter AB51 Active filters (Low Pass and High Pass) AB52 Active Band Pass Filter AB54 Tschebyscheff Filter AB56 Fiber Optic Analog Link AB57 Owen’s Bridge AB58 Anderson’s Bridge AB59 Maxwell’s Inductance Bridge AB64 RC – Coupled Amplifier with Feedback AB65 Phase Shift Oscillator AB66 Wien Bridge Oscillators AB67 Colpitt Oscillator AB68 Hartley Oscillator AB80 RLC Series and RLC Parallel Resonance AB82 Thevenin’s and Maximum power Transfer Theorem AB83 Reciprocity and Superposition Theorem AB84 Tellegen’s Theorem AB85 Norton’s theorem AB89 Diode Clampers AB90 Two port network parameter AB91 Optical Transducer (Photovoltaic cell) AB92 Optical Transducer (Photoconductive cell/LDR) AB93 Optical Transducer (Phototransistor) AB96 Temperature Transducer (RTD & IC335) AB97 Temperature Transducer (Thermocouple) AB101 DSB Modulator and Demodulator AB102 SSB Modulator and Demodulator AB106 FM Modulator and Demodulator

………… and many more

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Theory Clippers : The circuit with which the waveform is shaped by removing (or clipping) a portion of the applied wave is known as a clipping circuits. This kind of processing is useful for signal shaping, circuit protection, radars, digital and other electronic systems. In other words clippers have the ability to “clip” off a portion of the input signal without distorting the remaining part of the incoming wave. The simplest form of clipping circuits is Diode clippers. The basic of Diode clipper is – one resistance and a diode. These clippers can remove signal voltages above or below a specified level .Depending on the orientation of the diode, clippers are classified as-

1. Positive clippers 2. Negative clippers

3. Combination clippers There are two general categories of clippers-

1. Series clippers

2. Parallel clippers

Positive clippers : A positive clipper is that which removes the positive half-cycles of the input voltage figure 1 shows the circuit of positive clipper using a diode.

Figure 1

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How the circuit works ? During the positive half cycle, the diode turns on and looks like a short across the output terminals .Ideally, the output voltage is zero. On the negative half cycle, the diode is open. In that case, a negative cycle appears across the output. But practically silicon diode takes 0.7V for conduction and a germanium diode takes 0.3V for conduction. This 0.7V and 0.3V is called clipping level or reference level of diode. Therefore the clipping level is not zero, but 0.7V. Suppose the input signal has a peak value of 10V, the output of clipper will look like figure 2.

Figure 2

Negative clippers : A negative clipper is that which removes the negative half-cycles of the input voltage. If we reverse the polarity of the diode in positive clipper circuit, we get a negative clipper. Figure shows the circuit of negative clipper. The clipping level is at -0.7V. Suppose the input signal has a peak of 10V, the ideal output signal will look like as figure 3(a) and practical signal will look like as figure 3(b).

Figure 3a

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Figure 3b

These both positive and negative clippers circuits are the type of parallel clipper. The parallel configuration is defined as one where the diode is in a branch parallel to the load.

Series clippers : The series configuration is defined as one where the diode is in series with the load figure 4 (a) shows series negative clipper. During the positive half cycle, the diode turns on and looks like a short across the output terminals Ideally, complete positive cycle getting in output. On the negative half cycle, the diode is open. In that case, zero voltage appears across the output. This circuit ideally behaves as a half wave rectifier. The output signal looks like as figure 4(a).

Negative series clipper Figure 4a

Positive series clipper Figure 4b

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Figure 4(b) shows positive series clipper. The functionality of this circuit is exactly opposite to series negative clipper. During the positive half cycle of the input signal, diode is open this gives zero voltage at output. During the negative half cycle, the diode turns on and looks like a short across the output terminal .The output voltage is shown in figure 4 (b).

Biased Clipper : The reference level or clipping level of a positive clipper is ideally zero or 0.7V practically. If we want to change this reference level we add bias in the circuit.

Bias means applying an external voltage to change the reference level. By adding a DC voltage source in series with a diode, we can change the clipping level of positive clipper. But limitation is that a new V must be less than Vm of our normal operation. Figure 5 shows the circuit of biased positive clipper and biased negative clipper. Examine the output wave amplitude in both circuits.

Biased positive clipper Figure 5a

Biased Negative clipper

Figure 5b

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Combinational clipper : Combination clipper is a combination of biased positive and negative clipper. With a combination clipper, a portion of both positive and negative half cycles of input voltage can be removed or clipped. From figure 6 Diode D1 clips off positive parts above the positive bias level, and diode D2 clips off parts below the negative bias level. When positive input voltage is greater than +V1 , diode D1 conducts heavily while diode D2 remains reverse biased .Therefore, a voltage +V1 appears across the load. This output stays at +V1 as long as the input voltage exceeds +V1. On the other hand, during the negative half cycle, the diode D2 will conduct heavily and output stays at –V2 so long as the input voltage is greater than –V2. Between +V1 and –V2 neither diode is on. Therefore, in this condition, most of the input voltage appears across the load. Using batteries for low voltage is impractical. We give variable voltage source by vary a resistance. Figure 6 gives the circuit of combination clipper. Examine the amplitude of output wave.

Figure 6

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Experiment 1 Objective : Study of Parallel positive and parallel negative clipper

Equipments Needed : 1. Analog board AB88 2. DC power supplies +5V and -5V from external source or ST2612 Analog Lab. 3. Oscilloscope Caddo 802 or equivalent

4. Function generator 5. 2 mm patch cords

Circuit diagram : This experiment investigates the generation of positive and negative clipped waveform across the diode.

Figure 7

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Procedure :

• Connect +5V and -5V DC power supplies at their indicated position from external source or ST2612 Analog Lab.

1. With the help of function generator set sine wave of 1 KHZ frequency and amplitude 2Vpp approximately this is the input signal of clipper which we want to clip.

2. Give input signal to terminal a.

3. Monitor output signal at terminal b with the help of oscilloscope. This is the output of positive parallel clipper.

4. Disconnect input to terminal a and connect it to terminal c. 5. Monitor output signal at terminal d with the help of oscilloscope. This is the

output of negative parallel clipper.

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Experiment 2 Objective : Study of series positive and series negative clipper Equipments Needed : 1. Analog board AB88 2. DC power supplies +5V and -5V from external source or ST2612 Analog Lab. 3. Oscilloscope Caddo or equivalent 4. Function generator 5. 2 mm patch cords Circuit diagram : This experiment investigates the generation of positive and negative clipped waveform at the diode.

Figure 8

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Procedure :

• Connect +5V and -5V DC power supplies at their indicated position from external source or ST2612 Analog Lab.

1. With the help of function generator set sine wave of 1 KHZ frequency and amplitude 2Vpp approximately this is the input signal of clipper which we want to clip.

2. Give input signal to terminal e. 3. Monitor output signal at terminal f with the help of oscilloscope. This is the

output of positive series clipper. 4. Disconnect input to terminal e and connect it to terminal g.

5. Monitor output signal at terminal h with the help of oscilloscope. This is the output of Negative series clipper.

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Experiment 3 Objective : Study of combination clipper Equipments Needed : 1. Analog board AB88 2. DC power supplies +5V and -5V from external source or ST2612 Analog Lab. 3. Oscilloscope Caddo 802 or equivalent 4. Function generator

5. 2 mm patch cords

Circuit diagram : This experiment investigates the generation of positive and negative clipped waveform by combination clipper.

Figure 9

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Procedure : 1. With the help of function generator set sine wave of 1KHZ frequency and

amplitude 10Vpp approximately this is the input signal of clipper which we want to clip.

2. Give input signal to terminal k. 3. Monitor output signal at terminal m, with the help of oscilloscope.

4. Turn the potentiometer near VA, on the board, to its fully clockwise position. This is the variable DC voltage which we want to add in series with diode to achieve a clipping level.

5. Turn the potentiometer near VB, on the board, to its fully clockwise position. This is the variable DC voltage which we want to add in series with diode to achieve a clipping level.

6. Vary the potentiometer and examine the effect of adding DC voltage at terminal m.

7. Examine the level of DC voltage at TP1 and TP2, with the help of AC/DC switch on the oscilloscope or multimeter.

8. If zero DC voltage is present on TP2 and only vary TP1 at that time circuit act like as positive biased clipper. Examine the output at terminal m.

9. If zero DC voltage is present on TP1 and only vary TP2 at that time circuit act like as negative biased clipper. Examine the output at terminal m.

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Warranty 1. We guarantee the product against all manufacturing defects for 24 months from

the date of sale by us or through our dealers. Consumables like dry cell etc. are not covered under warranty.

2. The guarantee will become void, if

a) The product is not operated as per the instruction given in the operating manual.

b) The agreed payment terms and other conditions of sale are not followed.

c) The customer resells the instrument to another party. d) Any attempt is made to service and modify the instrument.

3. The non-working of the product is to be communicated to us immediately giving full details of the complaints and defects noticed specifically mentioning the type, serial number of the product and date of purchase etc.

4. The repair work will be carried out, provided the product is dispatched securely packed and insured. The transportation charges shall be borne by the customer.

For any Technical Problem Please Contact us at [email protected]

List of Accessories

1. 2mm Patch Cord (Red) 16” ................................................................ 2 Nos. 2. 2mm Patch Cord (Black) 16”.............................................................. 3 Nos. 3. 2mm Patch Cord (Blue) 16” ............................................................... 2 Nos.

4. e-Manual..............................................................................................1 No.

Updated 26-06-2009

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