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Semiconductor Electronic: Material, Devices And Simple Circuits — Physics STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 SciencePhysicsSemiconductor Electronic: Material, Devices And Simple Circuits5 Marks
Question
Consider a box with three terminals on top of it as shown in Fig (a):

Three components namely, two germanium diodes and one resistor are connected across these three terminals in some arrangement. A student performs an experiment in which any two of these three terminals are connected in the circuit shown in Fig. (b).

The student obtains graphs of current-voltage characteristics for unknown combination of components between the two terminals connected in the circuit. The graphs are

  1. When A is positive and B is negative,

  1. When A is negative and B is positive,

  1. When B is negative and C is positive,

  1. When B is positive and C is negative,

  1. When A is positive and C is negative,

  1. When A is negative and C is positive,

From these graphs of current - voltage characteristic shown in Fig. (c) to (h), determine the arrangement of components between A, B and C.

✓

Answer

The V-I characteristics of these graph is discussed in points:

  1. In V-I graph of condition (i), a reverse characteristics is shown in fig. (c).

Here A is connected to n-side of p-n junction I and B is connected top-side of p-n junction I with a resistance in series.

  1. In V-I graph of condition (ii), a forward characteristics is shown in fig. (d), where 0.7 V is the knee voltage of p-n junction I. 1/slope = (1/1000)Ω.

It means A is connected to n-side of p-n junction I and B is connected to p-side of p-n junction I and resistance R is in series of p-n junction I between A and B.

  1. In V-I graph of condition (iii), a forward characteristics is shown in figure (e) , where 0.7 V is the knee voltage. In this case p-side of p-n junction II is connected to C and n-side of p-n junction II to B.
  2. In V-I graphs of conditions (iv), (v), (vi) also concludes the above connection of p-n junctions I and II along with a resistance R.

Thus, the arrangement of p-n I, p-n II and resistance R between A, B and C will be as shown in the figure.

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