V-I AND I-V CONVERTER ANALOG LAB EXPERIMENT BOARD Ver. 1.0 An ISO 9001: 2000 company 94-101, Electronic Complex, Pardesipura INDORE-452010, India.
Tel.: 91-731-2570301 Fax: 91-731-2555643 Email: info@scientech.bz Web: www.scientech.bz Scientech Technologies Pvt. Ltd. 2
V-I AND I-V CONVERTER AB-30 TABLE OF CONTENTS 1. Introduction 3 2. Theory 5 3. Experiment 1 9 To study Op-amp as Voltage to Current converter (Floating output and Grounded load output) 4. Experiment 2 13 To study Op-amp as Current to Voltage Converter. Datasheet 16 5. Warranty 18 6. List of service Centers 19 7. List of Accessories with AB-30 20 Scientech Technologies Pvt. Ltd. 3
INTRODUCTION AB-30 is a compact, ready to use V-I AND I-V CONVERTER experiment board. This board is useful for students to understand the working and operation of op-amp as signal conveter. It can be used as stand alone unit with external DC power supply or can be used with SCIENTECH ANALOG LAB ST-2612 which has built in DC power supply, AC power supply, function generator, modulation generator, continuity tester, toggle switches, and potentiometer. List of Boards : Model AB-01 AB-02 AB-03 AB-04 AB-05 AB-06 AB-07 AB-08 AB-09 AB-15 AB-16 AB-17 AB-18 AB-19 AB-21 AB-22 AB-23 AB-25 AB-28 AB-29 AB-31 AB-32 AB-33 AB-34 AB-38 AB-40 AB-41 Name Diode characteristics (Si, Zener, LED) Transistor characteristics (CB NPN) Transistor characteristics (CB PNP) Transistor characteristics (CE NPN) Transistor characteristics (CE PNP) Transistor characteristics (CC NPN) Transistor characteristics (CC PNP) FET characteristics Rectifier Circuits Common Emitter Amplifier Common Collector Amplifier Common Base Amplifier RC-Coupled Amplifier Cascode Amplifier Class A Amplifier Class B Amplifier (push pull emitter follower) Class C Tuned Amplifier Phase Locked Loop (FM Demodulator & Frequency Multiplier/Divider) Multivibrators (Astable / Monostable) F-V and V-F Converter Zener Voltage Regulator Transistor Series Voltage Regulator Transistor Shunt Voltage Regulator DC Ammeter DC Voltmeter Op-amp Characteristics Differential Amplifier (Transistorized) Scientech Technologies Pvt. Ltd. 4
AB-42 AB-43 AB-44 AB-45 AB-51 AB-52 AB-53 AB-56 AB-65 AB-66 AB-67 AB-81 AB-82 AB-83 AB-84 AB-90 AB-91 AB-92 AB-93 Operational Amplifier (Inverting / Noninverting / Differentiator) Operational Amplifier (Adder/Scalar) Operational Amplifier (Integrator/Differentiator) Schmitt Trigger and Comparator Active filters (Low Pass and High Pass) Active Band Pass Filter Notch Filter Fiber Optic Analog Link Phase Shift Oscillator Wien Bridge Oscillators Colpitt Oscillator Kirchoff s Laws (Kirchoff s Current Law & Kirchoff s Voltage Law) Thevenin s and Maximum power Transfer Theorem Reciprocity and Superposition Theorem Tellegen s Theorem Two port network parameter Optical Transducer (Photovoltaic cell) Optical Transducer (Photoconductive cell/ldr) Optical Transducer (PhotoTransistor). and many more Scientech Technologies Pvt. Ltd. 5
THEORY Operational amplifier is a direct-coupled high-gain amplifier usually consisting of one or more differential amplifiers and usually followed by a level translator and an output stage. The output stage is generally a pushpull or push-pull complementary-symmetry pair. An operational amplifier is available as a single integrated circuit package. The operational amplifier is a versatile device that can be used to amplify DC as well as AC input signals and was originally designed for performing mathematical operations such as addition, subtraction, multiplication, and integration. Thus the name operational amplifier stems from its original use for these mathematical operations and is abbreviated to op-amp. With the addition of suitable external feedback components, the modern day op-amp can be used for a variety of applications, such as AC and DC signal amplification, active filters, oscillators, comparators, regulator, regulators, and others. The op-amp may be used as a voltage to current converter and current to voltage converter for both ac as well as dc input signal. This is explained as follows Voltage-to-Current Converter : Op-amp circuit as voltage to current converter can be used in two configurations 1. Output load floating 2. Output grounded load The very first configuration is op-amp with floating load (as shown in fig.1). In this circuit the feedback resistance will act as a load and as it is not connected to ground it will be called as floating. The input voltage will be applied to the non-inverting input of op-amp and the feedback voltage across resistance R L will drive the inverting input terminal. This circuit will also be called as Current-series negative feedback amplifier as the feedback voltage across R L (applied to inverting terminal) Scientech Technologies Pvt. Ltd. 6
depends on the output current i out and is in series with the input difference voltage V id. According to Kirchoff s volyage law for input loop, V in = V id + V f V-I Converter with output load floating But V id = 0, and op-amp gain is considered large enough, hence Fig.1 Or, V in = V f V in = R L x i out V in i out = ------- R L..(1) This means in the circuit of fig.1 an input voltage V in can be converted into an output current. If the R L is a precision resistance then output current will be precisely fixed. The second configuration of voltage to current converter is that in which one terminal of load is grounded and the load current is controlled be an input voltage. The circuit is as shown in fig.2. Scientech Technologies Pvt. Ltd. 7
According to Kirchoff s Voltage law, V-I Converter with grounded load Fig.2 Therefore, I 1 +I 2 =I L V in V 1 V O V 1 ------------ + ------------ = I L R R V in + V O 2V 1 = I L R V in + V O I L R V 1 = ---------------------- R Since op-amp is connected in non-inverting mode, the gain of the circuit will be 2. then the output voltage is V O = 2V 1 = V in + V O I L R V in = I L x R V in(r.m.s. value) i L = -------..(2) R This means that the load current depends on the input voltage V in and resistor R (all resistances are of equal value). Applications of V-I Converters : Low voltage dc-to-ac voltmeter Diode matched finders Light Emitting Diodes (LEDs) Zener diode Testers. Scientech Technologies Pvt. Ltd. 8
Current to Voltage Converter : Op-amp circuit working as current to voltage converter is as shown in fig.3a. Here the input current which is to be converted into output equivalent voltage is applied to the inverting input terminal of op-amp and hence the circuit will work as inverting amplifier. As we know the gain of inverting amplifier is given by, Therefore, However, since V 1 = 0V and V 1 = V 2 A v = V out = - R F V in R 1 V out = -V in x R F R 1 I in = V in / R 1 And V out = -I in x R F..(3) Fig.3a I-V Converter Fig.3b This means that if we replace the Vin and R1 combination by a current source Iin as shown in fig.3b the output voltage Vout becomes proportional to the input current Iin. In other words the circuit converts the input current Scientech Technologies Pvt. Ltd. 9
into proportional output voltage. In our AB-30 board we have used the same logic. Applications of I-V Converter : Sensing currents form photodetectors. In Digital to Analog Converters. EXPERIMENT 1 Object : To study the Op-amp as Voltage to Current Converter. Apparatus Required : 1. Analog board AB-30. 2. DC power supply +12V, -12V and variable dc supply of 0-5V from external source or ST-2612 Analog Lab. 3. Function Generator. 4. Ammeter. 5. 2mm patch chords. Circuit Diagram : Circuit used to study the operation of V-I Converter is shown below : Scientech Technologies Pvt. Ltd. 10
Fig. 4 Scientech Technologies Pvt. Ltd. 11
Procedure : Connect +12V and -12V dc power supplies at their indicated position from external source or ST-2612 Analog Lab. First we will study the V-I conversion for floating load configuration. 6. Connect a 0-5V variable dc signal at the non-inverting input (between points a and gnd) of Voltage to Current converter circuit of AB-30 board. Initially set the voltage to 0V dc. 7. Connect ammeter between points e and V out (this will connect a load at the output of op-amp and at the same time current flowing through the floating load can be observed on ammeter). 8. Gradually increase the variable dc supply at input from 0 to 5V (1V, 2V, 3V, 4V, 5V). 9. Note the respective output dc current displayed on ammeter in the following table. This will be the practical current value obtained from ammeter reading. 10. Also calculate theoretical value of output current form Eq.1 to crosscheck your results. I/p DC voltage (Vin) 1V 2V 3V 4V 5V O/p DC Current (Practical value) O/p DC Current from Eq.1 (Theoretical Value) 11. Remove dc signal applied at input and connect a 200Hz sine wave signal at the non-inverting input (between points a and gnd) of Voltage to Current converter circuit of AB-30 board. Initially set the voltage to 0Vp-p. Scientech Technologies Pvt. Ltd. 12
12. Gradually increase the variable dc supply at input from 0 to 5Vp-p (1Vp-p, 2Vp-p, 3Vp-p, 4Vp-p, and 5Vp-p). 13. Note the respective output ac current observed on ammeter in the following table. This will be the practical current value obtained from ammeter reading. 14. Also calculate theoretical value of output current form Eq.2 to crosscheck your results. I/p AC voltage (Vin) R.M.S. I/p Current Vrms=Vp-p/ 2 2 O/p AC Current (Practical value) O/p AC Current from Eq.2 (Theoretical Value) 1Vp-p 2Vp-p 3Vp-p 4Vp-p 5Vp-p Now we will study the V-I conversion for grounded load configuration. 1. Connect points e and V out using 2mm patch cord. 2. Connect point a and b using a 2mm patch cord. 3. Connect ammeter between points c and d (this will connect a load R L to the circuit and at the same time current flowing through the grounded load can be observed on ammeter). 4. Connect a 0-5V variable dc signal at the input (between points V in and gnd) of Voltage to Current converter circuit of AB-30 board. Initially set the voltage to 0V dc. 5. Gradually increase the variable dc supply at input from 0 to 5V (1V, 2V, 3V, 4V, 5V). Scientech Technologies Pvt. Ltd. 13
6. Note the respective output dc current displayed on ammeter in the following table. This will be the practical current value obtained from ammeter reading. 7. Also calculate theoretical value of output current form Eq.1 to crosscheck your results. I/p DC voltage (Vin) 1V 2V 3V 4V 5V O/p DC Current (Practical value) O/p DC Current from Eq.1 (Theoretical Value) 8. Remove dc signal applied at input and connect a 200Hz sine wave signal at the non-inverting input (between points a and gnd) of Voltage to Current converter circuit of AB-30 board. Initially set the voltage to 0Vp-p. 9. Gradually increase the variable dc supply at input from 0 to 5Vp-p (1Vp-p, 2Vp-p, 3Vp-p, 4Vp-p, and 5Vp-p). 10. Note the respective output ac current observed on ammeter in the following table. This will be the practical current value obtained from ammeter reading. 11. Also calculate theoretical value of output current form Eq.2 to crosscheck your results. I/p AC voltage (Vin) R.M.S. I/p Current Vrms=Vp-p/ 2 2 O/p AC Current (Practical value) O/p AC Current from Eq.2 (Theoretical Value) 1Vp-p 2Vp-p Scientech Technologies Pvt. Ltd. 14
3Vp-p 4Vp-p 5Vp-p Object : EXPERIMENT 2 To study the Op-amp as Current to Voltage Converter. Apparatus Required : 1. Analog board AB-30. 2. DC power supply +12V, -12V and variable dc supply of 0-5V from external source or ST-2612 Analog Lab. 3. Ammeter. 4. Voltmeter / Oscilloscope. 5. Function Generator. 6. 2mm patch chords. Circuit Diagram : Circuit used to study the operation of I-V Converter is shown below : Scientech Technologies Pvt. Ltd. 15
c Fig. 4 Scientech Technologies Pvt. Ltd. 16
Procedure : Connect +12V and -12V dc power supplies at their indicated position from external source or ST-2612 Analog Lab. Connect 5V dc signal at the input (between points f and gnd) of Voltage to Current converter circuit of AB-30 board. 1. Connect ammeter between points g and h (this will display the current flowing through the op-amp, I in ). 2. Connect Voltmeter between sockets V out and gnd. 3. Vary the pot to vary the input current from 1mA, gradually upto 5mA (1mA, 2mA, 3mA, 4mA and 5mA) and note the respective voltage on voltmeter in the following table. This is the practical value of voltage. 4. Also calculate theoretical value of output voltage form Eq.3 to crosscheck your results. I/p DC Current (I in) 5mA 10mA 15mA 20mA 24mA O/p DC Voltage (Practical value) (V out) O/p DC Voltage from Eq.1 (V out) (Theoretical Value) 5. Remove dc signal applied at input and connect a 200Hz sine wave signal between points f and gnd) of Current to Voltage converter circuit of AB-30 board. Set the voltage to 3Vp-p. 6. Vary the pot to vary the input current from 1mA, gradually upto 15mA (1mA, 3mA, 5mA 15mA) and note the respective voltage on voltmeter in the following table. This is the practical value of voltage. 7. Also calculate theoretical value of output voltage form Eq.3 to crosscheck your results. Scientech Technologies Pvt. Ltd. 17
I/p AC Current (I in) 1mA 3mA 5mA 7mA 9mA 11mA 13mA 15mA O/p AC Voltage (V) (Practical value) (V out) O/p AC Voltage (V) from Eq.1 (V out) (Theoretical Value) DATASHEET Scientech Technologies Pvt. Ltd. 18
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WARRANTY 1) We guarantee the instrument against all manufacturing defects during 24 months from the date of sale by us or through our dealers. 2) The guarantee covers manufacturing defects in respect of indigenous components and material limited to the warranty extended to us by the original manufacturer, and defect will be rectified as far as lies within our control. 3) The guarantee will become INVALID. a) If the instrument is not operated as per instruction given in the instruction manual. b) If the agreed payment terms and other conditions of sale are not followed. c) If the customer resells the instrument to another party. d) Provided no attempt have been made to service and modify the instrument. 4) The non-working of the instrument is to be communicated to us immediately giving full details of the complaints and defects noticed specifically mentioning the type and sr. no. of the instrument, date of purchase etc. 5) The repair work will be carried out, provided the instrument is dispatched securely packed and insured with the railways. To and fro charges will be to the account of the customer. DESPATCH PROCEDURE FOR SERVICE Should it become necessary to send back the instrument to factory please observe the following procedure: 1) Before dispatching the instrument please write to us giving full details of the fault noticed. 2) After receipt of your letter our repairs dept. will advise you whether it is necessary to send the instrument back to us for repairs or the adjustment is possible in your premises. Dispatch the instrument (only on the receipt of our advice) securely packed in original packing duly insured and freight paid along with accessories and a copy of the details noticed to us at our factory address. Scientech Technologies Pvt. Ltd. 21
LIST OF SERVICE CENTERS 1. Scientech Technologies P. Ltd. 90, Electronic Complex Ph: (0731) 5202959 Pardesipura, Email: info@scientech.bz INDORE 452010 2. Scientech Technologies P. Ltd. First Floor, Ph.: (011) 26513912, 26864943 14, Uday Park, Fax: (011) 26864943. NEW DELHI 110049 Email: ndel@scientech.bz 3. Scientech Technologies P. Ltd. New no.2, Old no.10, 4 th street Ph.: (044) 52187548, 52187549 Venkateswara nagar, Adyar Fax: (044) 52187549 CHENNAI 600025 Email: chennai@scientech.bz 4. Scientech Technologies P. Ltd. 202/19, 4 th main street Ph.: (080) 51285011 Ganganagar, Fax: (080) 51285022 BANGALORE- 560032 Email: bangalore@scientech.bz 5. Scientech Technologies P. Ltd. 8,1st floor, 123-Hariram Mansion, Ph.: (022) 56299457 Dada Saheb Phalke Road Fax: (022) 24168767 Dadar (East) Email: stplmum@vsnl.net MUMBAI 400014 6. Scientech Technologies P. Ltd. 988, Sadashiv Peth, Ph.: (020) 24461673 Gyan Prabodhini Lane, Fax: (020) 24482403 PUNE 411030 Email: pune@scientech.bz 7. Scientech Technologies P. Ltd SPS Apartment, 1 st Floor Ph. +913355266800 2, Ahmed Maooji Street, E mail: kolkata@scientech.bz Behind Jaiswal Hospital, Liluah, Howrah-711204 W.B. Scientech Technologies Pvt. Ltd. 22
LIST OF ACCESSORIES 1. 2mm patch cord (red)..2 No. 2. 2mm patch cord (blue) 4 No 3. 2mm patch cord (black)..4 No Scientech Technologies Pvt. Ltd. 23