Discuss your measurement results in the lab report Figure 3. From the measurement of IC, what is the β of the BJT? Does this agree with the value from the datasheet and the β that you calculated in Step 1? If not, explain. Does this voltage value confirm active mode of operation? (Is the emitter-base junction forward biased and the collector-base junction reverse biased?) Determine IC at the collector of the transistor. Measure the voltage across the collector and emitter of the transistor. Make a plot of IC vs VCE for IB = 50 μ A, with the load line for the R 2 resistor on the same plot. From the IC vs VCE data taken in Step 1 for the 2N3904 BJT, determine a resistance, R 2, that will cause the BJT transistor to operate in the active region for IB = 50 μ A set V 1 = 5 V. Compare this value with the VCE ( sat) value from the datasheet. 3) If you then disconnect the Base, you should get a very high reading between Collector and Emitter. The Ohmmeter reading will decrease by a small amount. 2) Now connect the Collector to the Base. You should get a fairly low resistance reading. From the IC vs VCE data taken in Step 1 for the 2 N3904 BJT, determine a resistance, R 2, that will cause the BJT transistor to operate in the saturation region for IB = 50 μ A set V 1 = 5 V. 1) Connect an Ohmmeter to forward bias the B-E junction with the Collector open. There is some amount of voltage drop between the emitter and base, about 0.7V. It is necessary to have the positive collector voltage and greater than the transistor’s emitter voltage to have a proper current flow between the emitter and collector. Determine the voltage, V2, and resistance, R1, in Figure 3 such that 50 μ A will flow from the base to the emitter in the NPN BJT. Now the base terminal works as input, and the collector-emitter region serves as the output. Furthermore, any queries regarding this concept or electronics projects, please give your valuable suggestions by commenting in the comment section below.A. We believe that you have got a better understanding of this concept. This is all about different types of transistor configurations which includes common base, common collector and common emitter. Delta is used to specify a small changeįor instance, if the i/p current (IB) in a CE change from 50 mA to75 mA and the o/p current (IC) changes from 2.5mA to 3.6mA, the current gain (b) will be 44.įrom the above current gain, we can conclude that a change in base current generates a change in collector current which is 44 times larger. The current gain of the common emitter (CE) circuit is denoted with beta (β).It is the relationship between collector current and base current.The following formula is used to calculate the beta (β). The following table below shows the configurations of common emitter, common base and common collector transistors. In this kind of circuit, the emitter terminal is mutual to both i/p & o/p. The following diagram shows the configuration of CE transistor. This gives a good performance and it is frequently thought of as the most commonly used configurations. The gain of the both voltage and current can be defined as a medium, but the o/p is opposite to the i/p that is 1800 change in the phase. The circuit of CE transistor gives a medium i/p and o/p impedance levels. The common emitter transistor configuration is most widely used configuration. If we want to use the same transistor in a CC, we can calculate gamma by the following equation.Ĭommon Emitter Transistor Configuration (CE) Therefore, a variation in base current of this transistor will give a change in collector current that will be nine times as big. These relations are given below.įor instance, the current gain value of the common base value (α) is 0.90, then the beta value can be calculated as When the transistor is connected in any of three basic configurations such as CE, CB and CC then there is a relationship between alpha, beta and gamma. This gain is related to CB current gain that is beta (β), and gain of the CC circuit is calculated when the b value is given by the following formula The current gain of the CC circuit is denoted with (γ) and it is calculated by using the following formula. Common Collector Transistor Configuration The collector terminal is mutual to both i/p and o/p circuits. The following diagram shows the configuration of CC transistor. Offering a high i/p impedance & a low o/p impedance are commonly used as a buffer.The voltage gain of this transistor is unity, the current gain is high and the o/p signals are in phase. The common collector transistor configuration is also known as the emitter follower because the emitter voltage of this transistor follows the base terminal of the transistor. Common Collector Transistor Configuration (CC)
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