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M.KUMARASAMY COLLEGE OF ENGINEERINGPRESENTED BY:-GUIDED BY:-K.SHUNMATHI -12BEC2184A.SINDHUBARATHI -12BEC2186S.SURYA -12BEC2200T.M.TAMILSELVI -12BEC2206S.VANIPRIYA -12BEC2215S.SELVIAsst. professorDept of ECE

TOPIC:DIGITAL THERMOMETER USING

IC741

CONTENTSLinear IC.IC 741.Ideal characteristics.Inverting amplifier.Non inverting amplifier.Voltage follower.Digital thermometer.Advantages.Applications.

LINEAR ICSA linear integrated circuit is a solid-state device.Output is linear to input.CHARACTERIZATION:ANALOG: -Continuous input & output states DIGITAL: -Discrete input and output states.

IC7418 pin dual line package. Oldest and most popular Op-amp IC. High performance monolithic operational amplifier.Uses- integrator, differentiator, summing amplifier etc..,

PINS OF IC 74s1:Pin 1 (Offset Null): Offset voltage is nulled by opposite polarity to the offset. Pin 2 (Inverted Input): Input signals inverted at output . Pin 3 (Non-Inverted Input): Input signals processed normally without inversion.

Contd... Pin 4 (-V): Given to negative supply voltage terminal. Pin 5 (Offset Null): Same as pin 1. Pin 6 (Output): Output signal obtained as per given input signal . Pin 7 (+V): Given to positive supply voltage terminal. Pin 8 (N/C): The 'N/C' stands for 'Not Connected'.

Input impedance Ri = infinityOutput impedance Ro = zeroOpen loop voltage gain = infinityBandwidth = infinityCMRR = infinitySlew rate = infinity

Ideal characteristics op-amp

Input impedance: Voltage across RIN will be small if A0 is high. Current through RIN is small.For non-inverting configuration where ideal input current is zero.

11Output impedanceThe input set at zero, for non-inverting and inverting configurations are identical.Actual output impedance is VOUT/I.

Open loop voltage gain:

Ab is called loop gain.For Ab >>1,

CMRR:CMRR is a ratio of output to input of amplifiers

Ability to reject an equal signal on both of the inputsCMRR =20LOG(V0/Vin)

Slew rate:

High Slew Rate AD8014

Maximum Change in VoltageChange in TimeBandwidth The range of frequency at which an Op-Amp will function.(Ideal = )

INVERTING AMPLIFIERConnected to the inverting input through an input resistor. Non - inverting input connected to ground directly or through a biasing resistor.

ContdClosed loop voltage gain Av= -Rf \ R1 Output voltage is opposite of the input voltage.

NON INVERTING AMPLIFIERThe signal is connected directly to the non - inverting input. Rf and R1 form a voltage divider circuit As the output signal feed to the inverting input.

ContdClosed Loop Voltage Gain Av= 1+Rf\R1Ri = Ro (very high)

VOLTAGE FOLLOWERNon-inverting amplifier in which negative feedback is obtained by connecting output to inverting input.Since Rf = 0, the gain is 1 Vo =Vin.

DIGITAL THERMOMETERThis digital thermometer can measure temperatures up to 150Cwith an accuracy of 1C.

DIGITAL THERMOMETER IN IC 741

IC7805Self-contained fixed linear voltage regulator. The 7805 has a 5volt output.Positive voltage regulator

VOLTAGE REGULATORAn unregulated power source & regulates to the voltage of the voltage regulator.Used in electronic circuits due to their ease-of-use and low cost.

IC 7660Negative low-dropout regulator. Performs supply voltage conversions from +ve to -ve.

LOW DROP-OUT REGULATORSLDOs simple inexpensive way to regulate an output voltage Easy to design with and use. Suitable for the specific circuit conditions.

WORKING OF DIGITAL THERMOMETERIC 741 has a constant flow of current through the base-emitter junction transistor.Voltage of base-emitter junction of transistor is proportional to its temperature. Silicon diode can be instead of transistor.

Contd...Variation in voltage of base-emitter junction is amplified by 2nd operational amplifier. Before the temperature is displayed . Preset VR1 - set the zero-reading on the meter

Contd...

Preset VR2 - set the range of temperature measurementRegulated 5V power supply derivedVoltage regulator IC 7805 and Negative low-dropout regulator IC 7660. Circuit works off a 9V battery.

Contd...Assemble circuit on PCB Enclose in small plastic box. Calibrate using presets VR1 and VR2.

ADVANTAGES:Easy & faster to read .Shaking down the thermometer is eliminated. Broken glass & exposure to mercury is eliminated.

APPLICATIONS:Electrocardiogram AmplificationPiezoelectric TransducerUse charge amplifierPID Controller