Functional Module Report Gregory Crachiolo LM2901 Quad Voltage
Contents
1. Functional Module Description The functional module consists of the LM2901 Quad Voltage Comparator chip a Static resistor two potentiometers and one small light emitting diode LED The comparator chip requires a supply voltage 5 V and ground 0 V as well as the input and reference voltages The potentiometers are used to vary the input voltage by changing its internal resistance so as to set the reference and input voltages Resistors are used to protect the circuit as well as vary the output LM2901 Quad Voltage Comparator 6 5 18 04 Functional Module Report Gregory Crachiolo Wiring Instructions Table 1 Outline for circuit connections Red Supply to the comparator 5V Input to the potentiometers Supply to 3KO resistor Black Comparator to ground OV Potentiometers to ground LED to ground Yellow Potentiometers to input and reference terminals Output to resistor Resistor to LED LM2901 Chip Specifications Table 2 Comparator performance features LM2901 Comparator Features Voltage Range 2 36 Vdc or 1 18 Vdc Supply Current Drain 8 mA Input Biasing Current 25 nA Input Offset Current 5 nA Offset Voltage 3 mV Output Saturation Voltage 250 mV at4 mA Table 3 Maximum comparator ratings Absolute Maximum Ratings Supply Voltage 36 Vdc or 418 Vdc Differential Input Voltage 36 Vdc Storage Te2. 1 0 14 no 2 5 2 5 0 14 no 2 5 2 57 3 08 yes 2 5 4 3 08 yes List of Parts Table 6 Comparator circuit supply list Part Value Unit LM2901 Quad Voltage Comparator Chip N A N A Pull up Resistor 3000 Q Potentiometer 50 000 Q LED N A N A Voltage Box 5 V Breadboard N A N A Red Wire N A N A Black Wire N A N A Yellow Wire N A N A Voltmeter N A N A Picture 1 Comparator module construction LM2901 Quad Voltage Comparator 5 18 04 Functional Module Report Gregory Crachiolo References RIZZONI GIORGIO 2000 Principles and Applications of Electrical Engineering 3 Edition Boston MA McGraw Hill 2000 National Semiconductor LM2901 Comparator Data Sheet http cache national com ds LM LM139 pdf LM2901 Quad Voltage Comparator 10 5 18 04
3. significantly larger than the reference voltage the output voltage will be high the LED will illuminate For input voltages that are smaller than the reference voltage the output of the comparator will be low the LED will be off For the purposes in this laboratory the comparator becomes a light switch Comparators however are not mainly used for illumination The LED serves as a tool to visualize what is happening Without the LED the output could still be quantified However an LED allows observation of the output without making specific measurements For practical applications a microcontroller is connected to the output from a comparator The high or low voltage input to the microcontroller will cause different responses LM2901 Quad Voltage Comparator 4 5 18 04 Functional Module Report Gregory Crachiolo el gt OQ 2 Et e AN TNdA 109s1s9 di Q I99W0yu2 0d Figure 1 Circuit diagram for basic comparator function module application Theory and Predictions The internal composition of a voltage comparator is in essence a modified operational amplifier op amp circuit A more detailed explanation of op amps is provided in the corresponding module An important note about op amps is that they are integrated circuits An integrated circuit is a collection of individual and electronic circuits that are composed on a single wafer For the purposes of this module a thorough discussion of these
4. Functional Module Report Gregory Crachiolo USER MANUAL FOR THE LM2901 QUAD VOLTAGE COMPARATOR FUNCTIONAL MODULE LM2901 Quad Voltage Comparator 1 5 18 04 Functional Module Report Gregory Crachiolo TABLE OF CONTENTS Ts Index OF Figures os usw eins cede ee GE Ge a GE n SG Ge 3 Bs Imdexof ViDles iese ES EDEN EE SEE bed OM DE SOEKE SE we N EE 3 ig ei OR OE EE NE 4 5 4 Theory and Predictions iss eie ss oo ssees sede N ek Ge ss scien Ge EN ke be Ke GN ee 5 6 5 Functional Module Description cccccescccccccccccccsscescceeeces 6 6 Wiring Instructions sr ses desea Ee dee KG EN GE Ke GN Ed Dk ee 7 7 LM2901 Chip SpeeificatOnS sssddsss sesse dees seg sitesdeswe diocese dsdses veeses 7 8 LM2901 Connection Diagram ccccescceccccescccccccesccesccceees 8 9 SR DPAT ALUS evs sce ss oe de vedas estas E GE dua EG Ee GE ds 8 10 Testine Sedu nce ss EES ES ER EN DE N Ge Ge Ee N N ie o 8 9 EL EASE OF Parts ses sokicecwensccabebdsoddcacwiibicawaxasabebianeicasahavcouneasonious 9 TZ PRION COS ss cece conte RE EG EG Ee ued RE EG GE seid GN RE De 10 LM2901 Quad Voltage Comparator 2 5 18 04 Functional Module Report Gregory Crachiolo Index of Figures Figure 1 Circuit Diagram for Basic Comparator Function 00 5 Figure 2 Comparator Chip Schematic sceccesccsscessecceessecsees 8 Figure 3 Comparator Connection Diagram ccsscssesceescesceescees 8 Index of Tables Table 1 Wiring Ou
5. contents is not necessary For a comparator application as opposed to ground in a non inverting operational amplifier a reference voltage is applied to the negative terminal LM2901 Quad Voltage Comparator 5 5 18 04 Functional Module Report Gregory Crachiolo In this module and for most applications the reference voltage is held constant The comparator allows a current to flow through the LED if the difference between the input voltage and the reference voltage has a quantity greater than zero The value of the output voltage is dependent on the value of the voltage the pull up resistor is connected to as well as the static value of the pull up resistor If the input voltage is less than the reference voltage the current from the pull up resistor will enter the comparator and flow to ground thus leaving the LED turned off Be careful the current through the LED must not exceed its maximum capacity or the LED will burn out Also when calculating the reference voltage theoretically the voltage drop across the LED is approximately 1 7 V Note there is a buffer zone in which the comparator will not function if the input voltage is greater but very close to the reference voltage Therefore in order for the circuit to operate properly there must be a significant difference between the two For example observe the experimental results table 5 for an input voltage 06 V above the reference voltage the LED experiences no current
6. mperature Range 65 C to 150 C Lead Temperature soldering 10 sec 260 C Operating Temperature Range 40 C to 85 C LM2901 Quad Voltage Comparator 7 5 18 04 Functional Module Report Gregory Crachiolo LM2901 Connection Diagram OUTPUT 3 OUTPUT 4 GND INPUT 4 INPUT 4 INPUT 3 OUTPUT 2 OUTPUT 1 v INPUT 1 INPUT 1 INPUT 2 TOP VIEW Figure 2 Comparator chip layout OUTPUT 2 OUTPUT 3 OUTPUT 1 OUTPUT 4 V GND INPUT 1 INPUT 4 INPUT 1 INPUT 4 INPUT 2 INPUT 3 INPUT 2 INPUT 3 Figure 3 Comparator connection diagram Apparatus Table 4 Functional equipment list Digital multimeter or equivalent voltmeter Power source Voltage box with 5V outlet and OV ground Constructed comparator circuit box Testing Sequence Once the comparator is connected to a power supply the circuit is ready for experimentation The reference voltage is set at half of the supply voltage 2 5V Connect the voltmeter to the input voltage and ground Adjust the input voltage while monitoring its level Notice the voltage at which the LED illuminates when the switch is on A table representing these results is found in table 5 LM2901 Quad Voltage Comparator 5 18 04 Functional Module Report Table 5 Testing seguence results for a varying input voltage Gregory Crachiolo V ref Volts V in Volts Vout Volts LED on 2 5
7. tlines is esse N SS ED EE DER sane NN ek op sk ER Ge SS eN bed 7 Table 2 Comparator Performance Features ccsccccescesseesseeees 7 Table3 Maximum Comparator Specifications scessecssessescees 7 Table 4 Functional Equipment List sesse ese esse ese sees see see see see ee ese 8 Table 5 Testing SEAUENEE ies eN Be AS EG N Ge Se EE N Gee SN EG N wi 9 Table 6 Supply EISt si ak ees vee GE Ee SE De GE GE Se OG GE De GN Ge EG 9 Index of Images Picture 1 Comparator Module Construction scccccssessecsceceeeee 9 LM2901 Quad Voltage Comparator 3 5 18 04 Functional Module Report Gregory Crachiolo Introduction Comparators have many practical applications which mostly include implementation of instrumentation systems However comparators may also be used for timing and vibration Many of the internal components of a voltage comparator are transistors Every transistor has a base emitter and collector The output of the comparator is connected to the collector of the last transistor in the chip Ifa pull up resistor is not connected to the output the comparator will not function properly This is called an open collector output For the situation in this module the input voltage is a DC signal The purpose of the comparator circuit is to evaluate the difference between the input voltage and the reference voltage In a comparator different input voltages yield different outputs For input voltages that are
Download Pdf Manuals
Related Search