Lab Report 3. NPN and PNP Transistors, Transistors Biasing, Q point stabilization PDF

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School of Engineering Department of Electrical and Electronic Engineering Analog Electronics Lab Report 3 Student Name: Sanzhar Askaruly Name of Lecturer: Alexander Ruderman Personal Tutor: Nazim Mir-Nasiri Astana, 2014 Introduction This lab session has a purpose of practical implementation of theor...

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School of Engineering Department of Electrical and Electronic Engineering

Analog Electronics Lab Report 3

Student Name: Sanzhar Askaruly Name of Lecturer: Alexander Ruderman Personal Tutor: Nazim Mir-Nasiri

Astana, 2014

Introduction This lab session has a purpose of practical implementation of theoretical knowledge about transistors. There are four parts in the work:   

NPN and PNP Transistors Transistors Biasing Q point stabilization

Apparatus The following equipment was used during the lab:   

MCM3/EV board Power supply PSLC or PS1-PSU/EV Accessories

As in the previous lab, the whole lab work is done with the MCM/EV board. The oscilloscope was used for the visualization of the waveforms. Screwdriver was used for the variable resistor configuration.

Work process 5. NPN and PNP Transistors Using jumpers the circuit shown in figure 1 was built.

Figure 1. Transistor circuit Base Current, IB (µA)

Collector Current, IC (mA)

20 40 60 80 100

8 13 19 25 27

hFE hFE = Ic/Ib 400 325 317 313 270

Q1. What range does hFE lie in? d) 100-400

Collector Current, Ic (mA)

Collector Current over Base Current 26 23 20 17 14 11 8 20

40

60

80

100

Base Current, Ib, (µA)

As it can be seen from the graph, collector current steadily increases with the increase in base current. Only when the base current exceeds 80 µA, the coefficient hFE starts to decrease. 6. Transistors Biasing Next, with the help of jumpers the circuit shown in figure 2 was built.

Figure 2. Transistor Biasing Circuit

𝐼𝑐𝑠𝑎𝑡 =

𝑉𝐶𝐶 − 𝑉𝐶𝐸𝑄 20 − 0 = = 42.68 𝑚𝐴 𝑅2 468.6 𝑚𝐴

The cut-off voltage was determined to be VCEM = 19.99 V Q2. What is the voltage VCE in saturation condition? e) 0.2 V

7. Q Point Stabilization 7.1. Stabilization circuit with RE Further, the circuit shown in figure 3 was built.

Figure 3. Stabilization circuit with RE Initially, VBE = 622 mV, IC = 11 mA and VO was found to be 598 mV. During the experiment, we tried to increase the temperature by connecting power to the heating resistor. As a result, transistor T5 was heated. As we noted, the following was observed: Q3. When the temperature increases what happens to this voltage and current? d) the current increases and the voltage drops After the, heating resistor was removed. Connecting J11 jumper, we measured IB current using ammeter. Collector current stays constant. As a result, IC = 10 mA and IB = 26 µA. Therefore, current gain was calculated: ℎ𝐹𝐸 =

𝐼𝐶 𝐼𝐵

= 385.

Q4. What is the calculated current gain? e) hFE > 150 Further, after disconnection of J10 and J11 jumpers, the resistance RBM was measured. The equivalent base resistance is estimated using this formula:

RBM was measured to be 32.7 kOhm. 27.6 𝑘𝑂ℎ𝑚 × [(89.4 − 27.6)𝑘𝑂ℎ𝑚 + 32.7 𝑘𝑂ℎ𝑚] 𝑅𝐵𝑀 = = 21.34 𝑘𝑂ℎ𝑚 [89.4 + 32.7]𝑘𝑂ℎ𝑚 After that stability factor is found from:

Therefore, 𝑆𝑣 = −

1 = −0.023 21.34 𝑘𝑂ℎ𝑚 385 + 100 𝑂ℎ𝑚

Q5. What is the stability factor Sv? c) between -1 and 0 7.2. Stabilization circuit with collector-base resistance

Figure 4. Stabilization circuit with collector-base resistance Initially, collector current was configured to 5mA. Q6. The variations of IC are smaller when the feedback resistor R8 is inserted. No Answer. I did not understand the meaning of question asked. I tried to simulate without R8 resistor and using R8 resistor. In both, cases the graph shows increasing pattern. However, there is discrepancy after 6V is reached by Vcc. The plot below provided below describes Vcc to Ic relation. When there is no resistor R8:

The same graph, but with feedback resistor R8 is place:...