C12-Ch14-JEE-HOTS.docx

**Semiconductor and Electronics -- JEE HOTS** 1. A silicon speciman is made into a *P-*type semi-conductor by dopping, on an average, one Indium atom per silicon atoms. If the number density of atoms in the silicon specimen is then the number of acceptor atoms in silicon per cubic cent...

**Semiconductor and Electronics -- JEE HOTS** 1. A silicon speciman is made into a *P-*type semi-conductor by dopping, on an average, one Indium atom per silicon atoms. If the number density of atoms in the silicon specimen is then the number of acceptor atoms in silicon per cubic centimetre will be **\[MP PMT 1993, 2003\]** 2. The probability of electrons to be found in the conduction band of an intrinsic semiconductor at a finite temperature **\[IIT-JEE 1995; DPMT 2004\]** \(a) Decreases exponentially with increasing band gap \(b) Increases exponentially with increasing band gap \(c) Decreases with increasing temperature \(d) Is independent of the temperature and the band gap 3. The typical ionisation energy of a donor in silicon is **\[IIT-JEE 1992\]** \(a) (b) 4. In *PN*-junction diode the reverse saturation current is *amp* at The forward current for a voltage of is **\[MP PMT 1993\]** \(a) (b) \(c) (d) 5. When a potential difference is applied across, the current passing through **\[IIT-JEE 1999\]** \(a) An insulator at is zero \(b) A semiconductor at is zero \(c) A metal at is finite \(d) A *P-N* diode at is finite, if it is reverse biased 6. A 2*V* battery is connected across the points *A* and *B* as shown in the figure given below. Assuming that the resistance of each diode is zero in forward bias and infinity in reverse bias, the current supplied by the battery when its positive terminal is connected to *A* is **\[UPSEAT 2002\]** 7. In the circuit, if the forward voltage drop for the diode is 0.5*V*, the current will be **\[UPSEAT 2003\]** 8. A *P*-type semiconductor has acceptor levels 57 *meV* above the valence band. The maximum wavelength of light required to create a hole is (Planck's constant *h* = *J-s*) **\[MP PET 1995\]** 9. Current in the circuit will be **\[CBSE PMT 2001\]** 10. The diode used in the circuit shown in the figure has a constant voltage drop of 0.5 *V* at all currents and a maximum power rating of 100 *milliwatts*. What should be the value of the resistor *R*, connected in series with the diode for obtaining maximum current **\[CBSE PMT 1997\]** 11. For a transistor amplifier in common emitter configuration for load impedance of 1 *k*Ω (*h~fe~* = 50 and *h~oe~* = 25 *μA/V*) the current gain is **\[AIEEE 2004\]** 12. In the following common emitter configuration an *NPN* transistor with current gain *β* = 100 is used. The output voltage of the amplifier will be **\[AIIMS 2003\]** 13. In semiconductor the concentrations of electrons and holes are 8 × 10^18^/*m*^3^ and 5 × 10^18^/*m* respectively. If the mobilities of electrons and hole are 2.3 *m*^2^/*volt-sec* and 0.01 *m*^2^/*volt-sec* respectively, then semiconductor is 14. A sinusoidal voltage of peak value 200 *volt* is connected to a diode and resistor *R* in the circuit shown so that half wave rectification occurs. If the forward resistance of the diode is negligible compared to *R* the *rms* voltage (in *volt*) across *R* is approximately 15. The junction diode in the following circuit requires a minimum current of 1 *mA* to be above the knee point (0.7 *V*) of its I-V characteristic curve. The voltage across the diode is independent of current above the knee point. If *V~B~* = 5 *V*, then the maximum value of *R* so that the voltage is above the knee point, will be 16. In the circuit given below, *V*(*t*) is the sinusoidal voltage source, voltage drop *V~AB~*(*t*) across the resistance *R* is **\[IIT 1993\]** 17. The peak voltage in the output of a half-wave diode rectifier fed with a sinusoidal signal without filter is 10 *V*. The dc component of the output voltage is **\[CBSE PMT 2004\]** 18. A transistor is used as an amplifier in *CB* mode with a load resistance of 5 *k* Ω the current gain of amplifier is 0.98 and the input resistance is 70 Ω, the voltage gain and power gain respectively are **\[Pb. PET 2003\]** 19. The Bohr radius of the fifth electron of phosphorus (atomic number = 15) acting as dopant in silicon (relative dielectric constant = 12) is 20. In the following circuits *PN*-junction diodes *D*~1~, *D*~2~ and *D*~3~ are ideal for the following potential of *A* and *B*, the correct increasing order of resistance between *A* and *B* will be 21. The circuit shown in following figure contains two diode *D*~1~ and *D*~2~ each with a forward resistance of 50 *ohms* and with infinite backward resistance. If the battery voltage is 6 *V*, the current through the 100 *ohm* resistance (in *amperes*) is **\[IIT-JEE 1997\]** 22. Find *V~AB~* **\[RPMT 2000\]** 23. A diode is connected to 220 *V* (*rms*) *ac* in series with a capacitor as shown in figure. The voltage across the capacitor is 24. A potential difference of 2*V* is applied between the opposite faces of a *Ge* crystal plate of area 1 *cm*^2^ and thickness 0.5 *mm*. If the concentration of electrons in *Ge* is 2 × 10^19^/*m*^3^ and mobilities of electrons and holes are and respectively, then the current flowing through the plate will be 25. The contribution in the total current flowing through a semiconductor due to electrons and holes are and respectively. If the drift velocity of electrons is times that of holes at this temperature, then the ratio of concentration of electrons and holes is 26. *Ge* and *Si* diodes conduct at 0.3 *V* and 0.7 *V* respectively. In the following figure if *Ge* diode connection are reversed, the valve of *V*~0~ changes by **\[Based on Roorkee 2000\]** 27. In the circuit shown in figure the maximum output voltage *V*~0~ is 28. In the following circuit find *I*~1~ and *I*~2~ \(a) 0, 0 \(b) 5 *mA*, 5 *mA* \(c) 5 *mA*, 0 \(d) 0, 5 *mA* 29. For the transistor circuit shown below, if *β* = 100, voltage drop between emitter and base is 0.7 *V* then value of *V~CE~* will be \(a) 10 *V* \(b) 5 *V* \(c) 13 *V* \(d) 0 *V* 30. In *NPN* transistor, 10^10^ electrons enters in emitter region in 10^--6^ *sec*. If 2% electrons are lost in base region then collector current and current amplification factor (*β*) respectively are \(a) 1.57 *mA*, 49 (b) 1.92 *mA*, 70 \(c) 2 *mA*, 25 (d) 2.25 *mA*, 100 31. The following configuration of gate is equivalent to **\[AMU 1999\]** 32. Figure gives a system of logic gates. From the study of truth table it can be found that to produce a high output (1) at *R*, we must have 33. The combination of gates shown below produces 34. The shows two NAND gates followed by a NOR gate. The system is equivalent to the following logic gate 35. The diagram of a logic circuit is given below. The output *F* of the circuit is represented by -------- ------- -------- ------- -------- ------- -------- ------- -------- --------- **1** **c** **2** **a** **3** **c** **4** **c** **5** **abd** **6** **a** **7** **a** **8** **c** **9** **b** **10** **b** **11** **d** **12** **c** **13** **a** **14** **b** **15** **a** **16** **d** **17** **b** **18** **a** **19** **a** **20** **c** **21** **b** **22** **a** **23** **d** **24** **d** **25** **a** **26** **b** **27** **b** **28** **d** **29** **c** **30** **a** **31** **b** **32** **c** **33** **d** **34** **b** **35** **c** -------- ------- -------- ------- -------- ------- -------- ------- -------- ---------