AReS

PART5Semiconductor

Experiment 3 :NPN Transistor

Theory

fig5-7

Fig. 5-7Structure and Sign of Transistor

A transistor is made by nearing two semiconductor junctions. Npn transistor is composed of two n materials and a p material, as in Fig. 5-7(a). One area of n material is called collector, and another area is called emitter, and the p area in the middle is called base. In Fig. 5-7 (b), direction of the arrow in the emitter terminal changes by the transistor being npn type or pnp type. As diodes, the front part of the arrow means the direction of the current between emitter and base.

When the emitter becomes a common terminal between the input and the output, it is called a common emitter(CE) structure, and the collector becomes output terminal and the base becomes input terminal. CE Forward current gain is the most important characteristic of the transistor and it is expressed as β or h_FE. Here, DC CE forward current gain is expressed as h_FE and defined as below.

h_FE=β=I_C/I_B

Fig. 5-8CE Circuit for AC Input Signal

Fig. 5-9CE Characteristic Curve

Fig. 5-8 shows the circuit that the base-emitter junction is forward biased, and base-collector junction is reverse biased in CE structure. The characteristic curve of the CE circuit of Fig. 5-7 is in Fig. 5-9.

The calculation of h_FE for Q point condition of I_B=20μA and I_C=2.2mA is as below.

h_FE=I_C/I_B =2.2mA/20μA=110

Along with h_FE, AC current gain for CE circiuit is used often, and it is defined as below.

h_fe=〖∆I〗_C/〖∆I〗_B | V_CE=Constan

In the transistor of Fig. 5-9, the AC current gain between Q point and A point is calculated as below.

h_fe=〖∆I〗_C/〖∆I〗_B | V_CE=Constant=(2.2mA-1.5mA)/(20μA-10μA)=0.7mA/10μA=70n

AC current gain h_fe is greatly different from DC current gain h_FE. In CE circuit, the current gain h_feis bigger to the AC signal. Also, this indicates the important voltage gain. Receiving a small signal and converting it to the big signal of same form is the most useful characteristic of the tran sistor. This process is called amplification.
According to Kirchhoff’s law of current, the current of transistor can be easily expressed as below.

I_B=I_E-I_C

The base current is smaller than that of emitter and that of collector, and is same as the difference between the two. In most calculations, it is ok to consider the emitter current and the collector current as same.

Experiment Process

Fig. 5-10NPN Transistor Characteristic Measuring Circuit

tab1

Experiment 5-3.1 NPN Transistor Characteristic Measurement
(In Circuit-3 of M-05, compose a circuit as in Fig. 5-10.)

Measuring (I_C) Flowing between R2 and Collector

1.Connection(Circuit-3 of M-05, Fig. 5-10)

1.Power Connection

Connect between V1 terminal of Variable Power on M04 board and VCE 5V~15V 3a(+) terminal of Circuit-3 with red line, and between com terminal and 3b(-) terminal with black line.

2.Measuring Instrument Connection

Ammeter Connection

Measure by using the current measurement function of separate Digital Multimeter.

Measuring the current (I_c) between R2 and collector: Connect the red line of Digital Multimeter to 3e terminal of Circuit-3 and the black line to 3f terminal.

Voltmeter Connection

Measuring the voltage of resistance R4’s both ends: Connect between 3i terminal of R4 and High terminal of Multimeter on the front panel with red line, and between 3j terminal and Low terminal with black line.

2.Wiring Diagram

flash

3.Measurement

1Choose dmm at the left menu of Touch LCD panel and click dcv.
2Choose dmm at the bottom of Touch LCD panel and click Variable Power, then 3 CH DC screen appears.
Choose on and click arrow right at the right of 00.0V to set up the input voltage as DC 10.0V and adjust the voltage value(voltage of R4’s both ends) indicated at Digital Multimeter as Variable Resistance R1 to make it 100mV, then record the current value of separate Digital Multimeter in table 5-5.

Execute the Variable Resistance R1 adjustment and measure by 100mV interval till 800mV.

Variable Resistance R1 is impressed with 5V, so adjust R1 to make I_B as 10μA. I_B is the base current and calculated by the formula below.
I_B=V_R2/R₂
Therefore, if I_B=10μA, V_R2=R₂×I_B=10×10³×10×10^-6. Therefore, if the voltage of R2’s both ends is 100mV, I_B is 10μA. When I_B=20μA, estimate by 200mV, and if I_B=80μA, estimate by 800mV for I_C.

Current I_C= 1mA
3After the measurement, click on red to cut off the output

Measuring (I_C) Flowing between R3 and Collector

1.Connection(Circuit-3 of M-05, Fig. 5-10)

1.Power Connection is same as [Measuring (I_C) Flowing between R2 and Collector]>Connection.

2.Measuring Instrument Connection

Ammeter Connection

Measure by using the current measurement function of separate Digital Multimeter.

Measuring the current (I_C) between R3 and collector: Connect the red line of Digital Multimeter to 3g terminal of Circuit-3 and the black line to 3n terminal.

Voltmeter Connection

<Voltmeter Connection> is same as [Measuring (I_C) Flowing between R2 and Collector]>Connection.

2.Wiring Diagram

flash

3.Measurement

1It is same as [Measuring (I_C) Flowing between R2 and Collector]>Measurement and record the measured value in the relevant column of table 5-5.

Current (I_C) = 1mA
2After the measurement, click on red to cut off the output.

4.Calculation

1. Draw a graph in Graph 5-3 using values of table 5-5, check out the collector current (I_C) flowing to R2, R3 when I_B is 40μA and calculate the current amplification factor.(when V_CE =10V)

tab2

Experiment 5-3.2 NPN Transistor Characteristic Measurement
(In Circuit-3 of M-05, compose a circuit as in Fig. 5-10.)

Changing the Base Current I_B as 40, 60, 80μA
and Measuring the Collector Current between R2 and Collector for each V_CE

1.Connection(Circuit-3 of M-05, Fig. 5-10)

1.Power Connection

Connect between V1 terminal of Variable Power on M04 board and VCE 5V~15V 3a(+) terminal of Circuit-e with red line, and between com terminal and 3b(-) terminal with black line.

2.Measuring Instrument Connection

Ammeter Connection

Measure by using the current measurement function of separate Digital Multimeter.

Measuring the current (I_C) between R2 and collector: Connect the red line of Digital Multimeter to 3e terminal of Circuit-3 and the black line to 3f terminal.

Voltmeter Connection

2.Wiring Diagram

flash

3.Measurement

1Choose dmm at the left menu of Touch LCD panel and click dcv. Choose quick launch at the bottom of Touch LCD panel and click Variable Power, then 3 CH DC screen appears.
Choose on and click arrow right at the right of 00.0V to set up the input voltage as DC 4.0V and adjust the voltage value(voltage of R4’s both ends) indicated at Digital Multimeter as Variable Resistance R1 to make it 200mV, then record the current value of separate Digital Multimeter in table 5-6.

Current (I_C)= 1.2mA

Click Variable Power and click arrow right at the right of 3 CH DC to adjust it to VCE voltage of table 5-6 and record the measured value of current (I_C) of separate Digital Multimeter in table 5-6.

If the voltage of R4’s both ends is out of 200mV(400mV, 600mV, 800mV), execute Variable Resistance R1 Adjustment, make it fit to the setup voltage, measure the current (I_C) flowing between R2 and Collector and record it.
2After the measurement, click on red to cut off the output.

Changing the Base Current (I_B) as 40, 60, 80μA
and Measuring the Collector Current between R3 and Collector for each V_CE

1.Connection(Circuit-3 of M-05, Fig. 5-9)

1.Power Connection is same as [Changing the Base Current (I_B) as 40, 60, 80μA and Measuring the Collector Current between R2 and Collector for each V_CE]

2.Measuring Instrument Connection

Ammeter Connection

Measure by using the current measurement function of separate Digital Multimeter.

Measuring the current (I_C) between R3 and collector: Connect the red line of Digital Multimeter to 3g terminal of Circuit-3 and the black line to 3h terminal.

Voltmeter Connection

<Voltmeter Connection> is same as [Changing the Base Current (I_B) as 40, 60, 80 μA and Measuring the Collector Current between R2 and Collector for each V_CE].

2.Wiring Diagram

flash

3.Measurement

1Execute same as [Changing the Base Current I_B as 40, 60, 80μA and Measuring the Collector Current between R2 and Collector for each V_CE]Measurement>1) process and record it in table 5-6.

Current (I_C)= 1.9mA
2After the measurement, click on red to cut off the output.

4.Calculation

1. Draw a graph in Graph 5-4 using values of table 5-6, draw a straight line between 10V of the voltage between collector- emitter(V_CE) and 6mA of the collector current (I_C), make the point where the base current (I_B) is 40uA as Q point and calculate the current amplification factor (h_FE) which is the DC current gain for Q point condition.

h_FE=I_C/I_B

2. Draw a vertical line to Q point and make the point where the base current (I_B) is 20uA as A point to calculate ΔI_B, ΔI_C and calculate AC current gain.

h_fe=(ΔI_C)/(ΔI_B )| V_CE=Constant

Experiment Result Report

result
Title	NPN Transistor	Date
Department		Id Number		Name

1. Experiment Result Table

Table 5-6

result_table
V_CE [V]
I_C [㎃]	I_B : 20㎂	R2
	I_B : 20㎂	R3
	I_B : 40㎂	R2
	I_B : 40㎂	R3
	I_B : 60㎂	R2
	I_B : 60㎂	R3
	I_B : 80㎂	R2
	I_B : 80㎂	R3

2. Review and Explanation

1) Draw a graph in Graph 5-3 using values of table 5-5, check out the collector current (I_C) flowing to R2, R3 when I_B is 40μA and calculate the current amplification factor. (when V_CE=10V)

h_FE=I_C/I_B

section paper Graph 5-3

2) Draw a graph in Graph 5-4 using values of table 5-6, draw a straight line between 10V of the voltage between collector-emitter(V_CE) and 6mA of the collector current (I_C), make the point where the base current(I_B) is 40uA as Q point and calculate the current amplification factor(h_FE) which is the DC current gain for Q point condition.

section paper Graph 5-4

h_FE=I_C/I_B

3) Draw a vertical line to Q point and make the point where the base current(I_B) is 20uA as A point to calculate ∆I_B, ∆I_C and calculate AC current gain.

h_fe=〖∆I〗_C/(∆I_B )

PART5Semiconductor

Experiment 3 :NPN Transistor

Theory

Experiment Process

Experiment 5-3.1 NPN Transistor Characteristic Measurement
(In Circuit-3 of M-05, compose a circuit as in Fig. 5-10.)

1.Connection(Circuit-3 of M-05, Fig. 5-10)

1.Power Connection

2.Measuring Instrument Connection

2.Wiring Diagram

flash

3.Measurement

1.Connection(Circuit-3 of M-05, Fig. 5-10)

1.Power Connection is same as [Measuring (I_C) Flowing between R2 and Collector]>Connection.

2.Measuring Instrument Connection

2.Wiring Diagram

flash

3.Measurement

4.Calculation

Experiment 5-3.2 NPN Transistor Characteristic Measurement
(In Circuit-3 of M-05, compose a circuit as in Fig. 5-10.)

1.Connection(Circuit-3 of M-05, Fig. 5-10)

1.Power Connection

2.Measuring Instrument Connection

2.Wiring Diagram

flash

3.Measurement

1.Connection(Circuit-3 of M-05, Fig. 5-9)

1.Power Connection is same as [Changing the Base Current (I_B) as 40, 60, 80μA and Measuring the Collector Current between R2 and Collector for each V_CE]

2.Measuring Instrument Connection

2.Wiring Diagram

flash

3.Measurement

4.Calculation

Experiment Result Report

1. Experiment Result Table

2. Review and Explanation

1) Draw a graph in Graph 5-3 using values of table 5-5, check out the collector current (I_C) flowing to R2, R3 when I_B is 40μA and calculate the current amplification factor. (when V_CE=10V)

3) Draw a vertical line to Q point and make the point where the base current(I_B) is 20uA as A point to calculate ∆I_B, ∆I_C and calculate AC current gain.

4) Explain the difference shown in graph 4 when the collector resistance is R2 and when it is R3.

5) Describe the operating point Q.

3. Discuss the experiment result.

PART5Semiconductor

Experiment 3 :NPN Transistor

Theory

Experiment Process

Experiment 5-3.1 NPN Transistor Characteristic Measurement (In Circuit-3 of M-05, compose a circuit as in Fig. 5-10.)

1.Connection(Circuit-3 of M-05, Fig. 5-10)

1.Power Connection

2.Measuring Instrument Connection

2.Wiring Diagram

flash

3.Measurement

1.Connection(Circuit-3 of M-05, Fig. 5-10)

1.Power Connection is same as [Measuring (IC) Flowing between R2 and Collector]>Connection.

2.Measuring Instrument Connection

2.Wiring Diagram

flash

3.Measurement

4.Calculation

Experiment 5-3.2 NPN Transistor Characteristic Measurement (In Circuit-3 of M-05, compose a circuit as in Fig. 5-10.)

1.Connection(Circuit-3 of M-05, Fig. 5-10)

1.Power Connection

2.Measuring Instrument Connection

2.Wiring Diagram

flash

3.Measurement

1.Connection(Circuit-3 of M-05, Fig. 5-9)

1.Power Connection is same as [Changing the Base Current (IB) as 40, 60, 80μA and Measuring the Collector Current between R2 and Collector for each VCE]

2.Measuring Instrument Connection

2.Wiring Diagram

flash

3.Measurement

4.Calculation

Experiment Result Report

1. Experiment Result Table

2. Review and Explanation

1) Draw a graph in Graph 5-3 using values of table 5-5, check out the collector current (IC) flowing to R2, R3 when IB is 40μA and calculate the current amplification factor. (when VCE=10V)

3) Draw a vertical line to Q point and make the point where the base current(IB) is 20uA as A point to calculate ∆IB, ∆IC and calculate AC current gain.

4) Explain the difference shown in graph 4 when the collector resistance is R2 and when it is R3.

5) Describe the operating point Q.

3. Discuss the experiment result.

Experiment 5-3.1 NPN Transistor Characteristic Measurement
(In Circuit-3 of M-05, compose a circuit as in Fig. 5-10.)

1.Power Connection is same as [Measuring (I_C) Flowing between R2 and Collector]>Connection.

Experiment 5-3.2 NPN Transistor Characteristic Measurement
(In Circuit-3 of M-05, compose a circuit as in Fig. 5-10.)

1.Power Connection is same as [Changing the Base Current (I_B) as 40, 60, 80μA and Measuring the Collector Current between R2 and Collector for each V_CE]

1) Draw a graph in Graph 5-3 using values of table 5-5, check out the collector current (I_C) flowing to R2, R3 when I_B is 40μA and calculate the current amplification factor. (when V_CE=10V)

3) Draw a vertical line to Q point and make the point where the base current(I_B) is 20uA as A point to calculate ∆I_B, ∆I_C and calculate AC current gain.