Radio, TV & Electr. Work Paper 3, May/June 2014
 Questions: 1 2 3 4 Main
Weakness/Remedies
Strength

Question 1

Question 1

AIM: To determine the common-emitter current-transfer characteristics.

1. Connect the circuit as shown in Figure 1.

Table 1

 V1(V) IC (mA) IB =  ( 1 3 5 7 9
1.  Close switches S1 and S2.
2.  Set V2 to 12 V.
3.  Set the input voltage (V1) to 1 V, measure and record in Table 1 the current (IC).
4.  Repeat step f for the other values of V1 in Table 1.
5.  Open switches S1 and S2.
6.  Complete Table 1.
7.  Plot a graph of IC (mA) on the vertical axis against IB ( on the horizontal axis.
8.  Determine the slope of the graph in step (j).
9.  Comment briefly on the value of the slope obtained in step (k) with the calculated average value of the d.c. current gain (IB).

The candidates were expected to connect the circuit as shown in Fig.1, measure and record in Tables 1,2 and 3 the different milliammeter and microammeter readings, plot the graph and make some deductions.

(c)                                                        Table 1

 V1(V) Ic(mA) IB(A) 1 5.30 – 5.70 30 177 – 190 3 5.30 – 5.70 230 23 – 25 5 5.30 – 5.70 430 12.3 – 13.3 7 5.30 – 5.70 630 8.4 – 9.05 9 5.30 – 5.70 830 6.4 -6.90 average =

The candidates, as reported, understood the question and carried out the actions required. As reported, some of the candidates had challenges in taking readings in microamperes range.

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