Physics of Devices — DU B.Sc. (Hons) Physics Previous Year Question Papers

(a) Derive an expression for the barrier potential and barrier width of a p-n junction diode. (b) In a Ge sample a donor type impurity is added to the extent of 1 atom per 10° Ge atoms. Find the concentration of electrons and holes in the sample. Given Ni = 2.5 x1013 cm 3 and number of Ge atoms is 4.41 x 1022 cm 3 (5) (a) Draw the circuit diagram and frequency response of the active first order low pass Butterworth filter. Obtain an expression for the high cutoff frequency and gain of the filter. (10) (b) Explain the working of a UJT with a suitable schematic diagram and draw its I-V characteristic curve (5) (a) Differentiate between DIAC and TRIAC. Sketch and explain the output characteristic curve of DIAC. (5) (b) Explain with appropriate diagrams the static and transfer characteristics of metal oxide semiconductor field effect transistor (MOSFET) (5) (c) Find the voltage gain magnitude of the wide band-pass filter for the given total pass band gain, input frequency, low cut-off frequency, and high cut-off frequency of 6, 750 Hz, 200 Hz and 1 kHz respectively. (5)