Revision analog electronics

REVISION ANALOG

ELECTRONICS

Prepared by: Cesar Mendoza Applied Technology Teacher

Revison:

1. Module 1: Semiconductor –Diode2. Module 2: BJT Transistor3. Module 3: Operational Amplifier4. Module 4: Application of

Semiconductor5. 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

_

+

Vin1 V in2

+V

-V

V out

Op Amp has 2 inputsInverting

Input

Non-Inverting

Input

Voltage Output

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.


_

+

Vin1 V in2

+V

-V

V out

Op Amp has voltage supply, +V and -V

Negative (-) supply voltage

Positive (+) supply voltage

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


Characteristic of Operational amplifier…….

1. High input impedance2. Output impedance is zero3. 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.

_

+

Vin1 V in2

+V

-V V out = A x (Vin2 – Vin1)Gain (A) = V out

V in

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 > Vin2 V out = -V

Op Amp as Comparator.

Example: The +V= 15V and; If Vin1= 4mV and –V = -15V

Vin2 = 6 mV

Therefore: Vin2 > Vin2 So, Vout= 15V

Op Amp compares Vin1 and Vin2:

If Vin 2 > Vin1 therefore: V out = +VIf Vin1 > Vin2 V out = -V


Operational

Amplifier

Pin Number or Configuration

Fig. LM 311 Op Amp IC

Fig. LM 741 Op Amp IC

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

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

Pin Number or Configuration

Other uses of Op Amp.

1. Inverting Amplifier2. Non inverting

amplifier3. Summing Amplifier4. Differential amplifier5. Voltage follower6. Integrator7. Differentiator

Revision Question1. ________________is an electronic devices

which amplifies small ac or dc signal and perform basic operation as addition, subtraction multiplication and so on.

2. ________________- input of Op Amp where the output is changed to opposite sign.

3. ________________ the open loop gain of Op Amp.

4. ________________ use of an Op Amp with no feedback. where it compares Vin2 and Vin2.

5. ________________ the arrangement of Pin of an integrated circuit of IC.

6. ________________ is the Pin number of the output of a LM741 operational amplifier.

Application of Op amp.


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…

Potentiometer of Variable Resistor

A

B

C

A

B

C

R1

R2

Vcc

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.

Temperature, deg C

Temperature, deg C

Resis

tanc

e ,

ohm

Resis

tanc

e ,

ohm

NTC PTC

Voltage Divider…

A

B

C

R1

The voltage VC changes the resistance of the Thermistor changes.

VB = Vcc x RNTC . R1 + RNTC

Vcc

Revision Question

6. ________________ a circuit that divided the voltage proportionally with the value of resistors connected in series.

7. _______________ a thermal resistor that converts temperature in change in resistance.

8. _______________ use of an Op Amp with no feedback. where it compares Vin2 and Vin2.

9. ________________ the arrangement of Pin of an integrated circuit of IC.

Voltage Divider…

A

B

C

R1

Vc = Vcc x RNTC . R1 + RNTC

Vcc

If R1 = 10,000 RNTC = 10,000 @ 30 deg C

VB = 10V x ( 10,000/20,000)VB = 5V

Voltage Divider…

A

B

C

R1

Vcc = 10V

If R1 = 10,000 RNTC = 10,000 @ 30 deg C

VB = 10V x ( 10,000/20,000)VB = 5V

If RNTC = 8,000 @ 50 deg C

VB = 10V x (8,000/ 18,000)VB = 4.44 V

So, Vin2 could be from 0-12V?

Potentiometer.

B

C

A

Vcc= 10V

IF Vcc = 10 V

Therefore: VBC = 0V – 10 V

V

Potentiometer.

B

C

A

Vcc= 10V

VBC = 0V

V

B

C

A

Vcc= 10V

VBC = 10V

V

Potentiometer.

B

C

A

Vcc= 10V

So, in the middle VBC = 5V

V

I will combine potentiometer circuit and the Voltage divider circuit with NTC

B

C

A

Vcc= 10V

A

B

C

R1

Vcc

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

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

So, if Vin2 > Vin3 = Vout = +12V

IN THIS FIGURE ONLY


IN THIS FIGURE ONLY

Voltage Output

The Vout = +12V will activate the Driver Transistors

What is Transistor? BJT?

BJT - is a three-terminal semiconductor device, whose operation depends upon the flow of electric charge carriers within the solid.

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

Transistor…

Transistor ID.

Low PowerSmall Packages

Medium PowerMedium Packages

High Powerbig Packages

Transistor Action…

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

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:

1. Switch2. Amplifier.

Small Base Current

Will Turn ON the Transistor

Transistor as switch…

When switch is closed:

1. Small base current is applied to the base.

2. LED B is DIM (small current)

3. Transistor is turned ON allowing emitter-collector current which is bigger.

4. LED C will have a bright light (big current)


IN THIS FIGURE ONLY

Voltage Output

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.

R Base

Small Current

Big current

Med Current

AC power Supply

Conclusion

We Learned About:1. Application of Semiconductor

Devices: transistor diode, etc..2. Learned the operation of transistor3. WE learn operational amplifier and

it uses.4. We make use of LED as indicator

of current.

Thank You For

Listening

What is voltage divider circuit?

Revision analog electronics

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