 # Revision analog electronics

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Revision analog electronics
Prepared by: Cesar Mendoza Applied Technology Teacher

Revison: Module 1: Semiconductor –Diode Module 2: BJT Transistor
Module 3: Operational Amplifier Module 4: Application of Semiconductor Module 5: Project

Project- automatic fan controller
Operational Amplifier

What is Operational Amplifier?
Operational Amplifier is an electronic devices which amplifies small ac or dc signal and perform basic operation as addition, subtraction multiplication and so on. Fig. Operational amplifier (LM741)

Operational Amplifier
Op Amp has 2 inputs Voltage Output Inverting Input +V _ Vin1 V out + V in2 -V Non-Inverting Input Inverting Input- the input where output will change to the opposite sign. Non-Inverting Input- the input where output will not change to the opposite sign.

Operational Amplifier
Op Amp has voltage supply, +V and -V Positive (+) supply voltage +V _ Vin1 V out + V in2 -V Negative (-) supply voltage

Operational Amplifier
OP-AMP is an IC or Integrated Circuit made of many components

Characteristic of Operational amplifier…….
High input impedance Output impedance is zero Open loop gain is high (10,000x)

What is the use of Operational Amplifier?
Operational Amplifier -amplifies small AC or DC Signal. Operational Amplifier can also do basic operation : add, subtract, multiply (amplify) etc.

+ +V _ Vin1 V out V in2 -V V out = A x (Vin2 – Vin1) Gain (A) = V out
Open Loop Gain = 100,000 x

Op Amp as Comparator. Op Amp compares Vin1 and Vin2:
If Vin 2 > Vin1 therefore: V out = +V If Vin1 > Vin V out = -V

Op Amp as Comparator. Op Amp compares Vin1 and Vin2: If Vin 2 > Vin therefore: V out = +V If Vin1 > Vin V out = -V Example: The +V= 15V and; If Vin1= 4mV and –V = -15V Vin2 = 6 mV Therefore: Vin2 > Vin So, Vout= 15V

Project- automatic fan controller
Operational Amplifier

Pin Number or Configuration
Fig. LM 311 Op Amp IC Fig. LM 741 Op Amp IC

Pin Number or Configuration
Pin Configuration is the assignment of Pin number with the corresponding use.

Pin Number or Configuration
Pin 1 and Pin 5: Offset null input; used to remove the Offset voltage (a small DC voltage that exists at the op-amp inputs that will contribute to a significant error at the output). Pin 2: Inverting input (-VIN); signals at this pin will be inverted at output Pin 6. Pin 3: Non-inverting input (+VIN); signals at pin 3 will be processed without inversion. Pin 4: Negative power supply terminal (-VCC). Pin 6: Output (VOUT) of the Op-Amp Pin 8: No connection (N\C), it is just there to make it a standard 8-pin package

Other uses of Op Amp. Inverting Amplifier Non inverting amplifier
Summing Amplifier Differential amplifier Voltage follower Integrator Differentiator

Revision Question ________________is an electronic devices which amplifies small ac or dc signal and perform basic operation as addition, subtraction multiplication and so on. ________________- input of Op Amp where the output is changed to opposite sign. ________________ the open loop gain of Op Amp. ________________ use of an Op Amp with no feedback. where it compares Vin2 and Vin2. ________________ the arrangement of Pin of an integrated circuit of IC. ________________ is the Pin number of the output of a LM741 operational amplifier.

Application of Op amp.

Project- automatic fan controller
Do you understand now the purpose of the operational amplifier in this circuit? Answer: To Compare input pin 3 and pin 2.

What is the Input in Pin 3 and Pin 2?
Voltage Divider Circuit (Reference)

What is the Input in Pin 3 and Pin 2?
Voltage Divider Circuit (Sensor)

Voltage Divider… Vcc A A R1 B C B R2 C
Potentiometer of Variable Resistor A A R1 B C B R2 C

So, Vin2 could be from 0-12V?

And Vin1 depends on the value of NTC?

What is NTC? NTC is a Thermistor or Thermal Resistor that converts Temperature to Change in Resistance. It has two (2) types; NTC and PTC NTC – Negative Temperature Coefficient. As temp increses, resistance Decrease. PTC – Positive Temperature Coefficient. As tempincrease, resistance increases. Resistance , ohm Resistance , ohm Temperature, deg C Temperature, deg C NTC PTC

Voltage Divider… VB = Vcc x RNTC . R1 + RNTC Vcc
The voltage VC changes the resistance of the Thermistor changes. A B C R1 VB = Vcc x RNTC . R1 + RNTC

Revision Question ________________ a circuit that divided the voltage proportionally with the value of resistors connected in series. _______________ a thermal resistor that converts temperature in change in resistance. _______________ use of an Op Amp with no feedback. where it compares Vin2 and Vin2. ________________ the arrangement of Pin of an integrated circuit of IC.

Voltage Divider… Vc = Vcc x RNTC . R1 + RNTC Vcc A R1 B C
If R1 = 10,000 RNTC = 30 deg C VB = 10V x ( 10,000/20,000) VB = 5V

Voltage Divider… Vcc = 10V If R1 = 10,000 A RNTC = 10,000 @ 30 deg C
B C R1 If R1 = 10,000 RNTC = 30 deg C VB = 10V x ( 10,000/20,000) VB = 5V If RNTC = 50 deg C VB = 10V x (8,000/ 18,000) VB = 4.44 V

So, Vin2 could be from 0-12V?

Potentiometer. V IF Vcc = 10 V Therefore: VBC = 0V – 10 V Vcc= 10V A B

Potentiometer. Vcc= 10V Vcc= 10V A A B B C C V V VBC = 10V VBC = 0V

Potentiometer. Vcc= 10V A B C V So, in the middle VBC = 5V

I will combine potentiometer circuit and the Voltage divider circuit with NTC
Vcc A B C R1 B C A Vcc= 10V

So, this 2 circuit is the input to the operational amplifier

So, this 2 circuit is the input to the operational amplifier
IN THIS FIGURE ONLY So, if Vin2 > Vin3 = Vout = +12V

So, if Vin2 > Vin3 = Vout = +12V
Voltage Output IN THIS FIGURE ONLY So, if Vin2 > Vin3 = Vout = +12V The Vout = +12V will activate the Driver Transistors

What is Transistor? BJT? Transistor is derived from the combination of two words, “Transfer-Resistance”. It means that it is a device, which transfers a low resistance into a circuit having high resistance BJT - is a three-terminal semiconductor device, whose operation depends upon the flow of electric charge carriers within the solid.

Transistor…

Transistor ID. Low Power Small Packages Medium Power Medium Packages
High Power big Packages

Transistor Action… Its emitter is its negative terminal.
The base is 0.7V (or slightly more) positive of its emitter The base is 0.7V (or slightly more) positive of its emitter The base is 0.7V (or slightly more) positive of its emitter Transistor Action… Its emitter is its negative terminal. The collector is several volts positive of its emitter. The base is 0.7V (or slightly more) positive of its emitter

Use of Transistor. Transistor is used as: Switch Amplifier.
Will Turn ON the Transistor Small Base Current

Transistor as switch… When switch is closed:
Small base current is applied to the base. LED B is DIM (small current) Transistor is turned ON allowing emitter-collector current which is bigger. LED C will have a bright light (big current)

So, if Vin2 > Vin3 = Vout = +12V
Voltage Output IN THIS FIGURE ONLY So, if Vin2 > Vin3 = Vout = +12V The Vout = +12V will activate the Driver Transistors

R Base So if the output of the OP Amp is Hi, it will provide base current to the transistor making it ON thus Energizing the Relay.

What is a Relay? Relay – an electrically operated switch. It is made of coil and set of contacts, NO NC.

AC power Supply Small Current Med Current R Base Big current

Conclusion We Learned About: Application of Semiconductor Devices: transistor diode, etc.. Learned the operation of transistor WE learn operational amplifier and it uses. We make use of LED as indicator of current.

Thank You For Listening

What is voltage divider circuit?