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1. BASIC ELECTRONICS PRESENTED BY- GARGI ROY ASSISTANT PROFESSOR ELECTRICAL ENGINEERING DEPARTMENT JIS COLLEGE OF ENGINEERING

2. TITLE: BASIC ELECTRONICS SUBJECT CODE - EE/S3/BE(for Diploma) CREDIT-4

3. COURSE OBJECTIVE To provide an introduction to the fundamentals of semiconductor physics and PN junction to follow the functioning of all semiconductor based devices. Understanding of the subject will provide skill for trouble shooting & testing of some basic electronic components and circuits

4. COURSE OUTCOME Students will be able to Describe the formation of P-N junction. Draw the characteristics of basic components like diode, transistor etc. Draw & describe the basic circuits of rectifier, filter, regulator & amplifier. Test diode and transistors. Read the data sheets of diode and transistors.

5. COURSE OVERVIEW TRANSISTOR CONNECTION (COMMON COLLECTOR )

6. INTRODUCTION The  Common Collector connection  is another type of bipolar junction transistor, (BJT) configuration, where the input signal is applied to the base terminal and the output signal taken from the emitter terminal. Thus the collector terminal is common to both the input and output circuits. This type of configuration is called Common Collector, (CC) because the collector terminal is effectively “grounded” or “earthed” through the power supply.

7. BASICS OF COMMON COLLECTOR CONNECTION In many ways the common collector configuration (CC) is the reverse of the common emitter (CE) configuration as the connected load resistor is changed from the collector terminal for R C  to the emitter terminal for R E . The common collector or grounded collector configuration is commonly used where a high impedance input source needs to be connected to a low impedance output load requiring a high current gain Sometimes common collector configuration is also referred to as emitter follower, voltage follower, common collector amplifier, CC amplifier, or CC configuration. This configuration is mostly used as a voltage buffer .

8. COMMON COLLECTOR CONFIGURATION The input supply voltage between base and collector is denoted by V BC while the output voltage between emitter and collector is denoted by V EC . In this configuration, input current or base current is denoted by I B and output current or emitter current is denoted by I E . The common collector amplifier has high input impedance and low output impedance. It has low voltage gain and high current gain. The power gain of the common collector amplifier is medium.

9. CURRENT AMPLIFICATION FACTOR ( γ ) The current amplification factor is defined as the ratio of the output current to the input current. In common collector configuration, the output current is emitter current I E , whereas the input current is base current I B . Thus, the ratio of change in emitter current to the change in base current is known as the current amplification factor . It is expressed by the Y. γ = ∆ I E / ∆ I B

10. RELATION BETWEEN Υ AND  𝝰 The  Υ  is the current amplification factor of common collector configuration and the  α  is current amplification factor of common base connection. γ = ∆ I E / ∆ I B --------------------------------- i ) 𝝰 = ∆ I C / ∆ I E --------------------------ii) I E = I B + I C ∆ I E = ∆ I B + ∆ I C ∆ I B = ∆ I E - ∆ I C Now, Substituting the value of ∆ I B in the equation i ) we get---

11. RELATION BETWEEN Υ AND  𝝰 γ = ∆ I E / ∆ I B γ = ∆ I E / ∆ I E - ∆ I C Dividing the numerator and denominator of R.H.S by ∆ I E ,we get- γ = γ = 1 / (1- 𝝰 ) This circuit is mainly used for amplification because of this arrangement input resistance is high, and output  resistance is very low. The voltage gain of the resistance is very low. This circuit arrangement is mainly used for impedance matching.

12. EXPRESSION OF COLLECTOR CURRENT

13. COMPARISON OF TRANSISTOR CONNECTION

14. INPUT CHARACTERISTICS The input characteristics describe the relationship between input current or base current (I B ) and input voltage or base-collector voltage (V BC ). The input current or base current (I B ) is taken along y-axis (vertical line) and the input voltage or base-collector voltage (V BC ) is taken along x-axis (horizontal line). To determine the input characteristics, the output voltage V EC  is kept constant at 3V and the input voltage V BC is increased from zero volts to different voltage levels . For each level of input voltage V BC,  the corresponding input current I B is noted . A curve is then drawn between input current I B and input voltage V BC at constant output voltage V EC  (3V ). The output voltage V EC is increased from 3V to different voltage level, say for example 5V and then kept constant at 5V. While increasing the output voltage V EC , the input voltage V BC is kept constant at zero volts.

15. OUTPUT CHARACTERISTICS The output characteristics describe the relationship between output current or emitter current (I E ) and output voltage or emitter-collector voltage (V EC ). The output current or emitter current (I E ) is taken along y-axis (vertical line) and the output voltage or emitter-collector voltage (V EC ) is taken along x-axis (horizontal line ). To determine the output characteristics, the input current I B is kept constant at zero micro amperes and the output voltage V EC is increased from zero volts to different voltage levels. For each level of output voltage V EC , the corresponding output current I E is noted. A curve is then drawn between output current I E and output voltage V EC at constant input current I B (0 μ A ). the input current (I B ) is increased from 0  μA  to 20  μA  and then kept constant at 20  μA . While increasing the input current (I B ), the output voltage (V EC ) is kept constant at 0 volts

16. OUTPUT CHARACTERISTICS After we kept the input current (I B ) constant at 20  μA , the output voltage (V EC ) is increased from zero volts to different voltage levels. For each level of output voltage (V EC ), the corresponding output current (I E ) is recorded. A curve is then drawn between output current I E and output voltage V EC  at constant input current I B  (20μA). This region is known as the active region of a transistor . This process is repeated for higher fixed values of input current I B (I.e. 40  μA , 60  μA , 80  μA  and so on ). In common collector configuration, if the input current or base current is zero then the output current or emitter current is also zero. As a result, no current flows through the transistor. So the transistor will be in the cutoff region. If the base current is slightly increased then the output current or emitter current also increases. So the transistor falls into the active region. If the base current is heavily increased then the current flowing through the transistor also heavily increases. As a result, the transistor falls into the saturation region.

17. TRANSISTOR PARAMETERS Dynamic input resistance ( r i ) Dynamic input resistance is defined as the ratio of change in input voltage or base voltage (V BC ) to the corresponding change in input current or base current (I B ), with the output voltage or emitter voltage (V EC ) kept at constant . The input resistance of common collector amplifier is high. Dynamic output resistance ( r o ) Dynamic output resistance is defined as the ratio of change in output voltage or emitter voltage (V EC ) to the corresponding change in output current or emitter current (I E ), with the input current or base current (I B ) kept at constant. The output resistance of common collector amplifier is low.

18. TRANSISTOR AS AN AMPLIFIER An amplifier circuit is used to amplify a signal. The transistor raises the strength of a weak signal and hence acts an amplifier. The transistor has three terminals namely emitter, base and collector. The emitter and base of the transistor are connected in forward biased and the collector base region is in reverse bias. The forward bias means the P-region of the transistor is connected to the positive terminal of the supply and the negative region is connected to the N-terminal and in reverse bias just opposite of it has occurred. The input signal or weak signal is applied across the emitter base and the output is obtained to the load resistor R C   which is connected in the collector circuit. The DC voltage V EE  is applied to the input circuit along with the input signal to achieve the amplification. The DC voltage V EE  keeps the emitter-base junction under the forward biased condition regardless of the polarity of the input signal and is known as a bias voltage.

19. TRANSISTOR AS AN AMPLIFIER When a weak signal is applied to the input, a small change in signal voltage causes a change in emitter current (or we can say a change of 0.1V in signal voltage causes a change of 1mA in the emitter current) because the input circuit has very low resistance. This change is almost the same in collector current because of the transmitter action. In the collector circuit, a load resistor R C  of high value is connected. When collector current flows through such a high resistance, it produces a large voltage drop across it. Thus, a weak signal (0.1V) applied to the input circuit appears in the amplified form (10V) in the collector circuit.

20. SUMMARY Introduction Common collector transistor Common collector configuration Current amplification factor Relation between current amplification for CC mode & current amplification factor for CB mode Expression of collector current Input Characteristics Output Characteristics Transistor parameters Transistor as an amplifier

21. ASSIGNMENT What is CC configuration? What are the applications of CC mode of transistor? What are the input and output characteristics of CC mode transistor?

22. REFERENCES https://www.instructables.com/ https://circuitglobe.com/ https://www.electrical4u.com/npn-transistor/ https://www.electronics-notes.com/

23. THANK YOU