UNIT III

HIGH FREQUENCY TRANSISTOR CIRCUITS : 
Hybrid-p Common Emitter transistor model, Hybrid p Conductances, Hybrid-p Capacitances,  Variation of  Hybrid p Parameters, CE Short Circuit Current Gain,  Current Gain with Resistive Load,  Gain- Band width product, Emitter Follower at High Frequencies.

REFERENCE BOOKS :

1.       Integrated Electronics – J. Millman and C.C. Halkias, McGraw-Hill, 1972.
2.       Micro Electronic Circuits – Sedra A.S. and K.C. Smith, Oxford University Press, 5th ed.
3.       Electronic Devices and Circuits - Theodore F. Bogart Jr., J. S. Beasley and G. Rico, Pearson  
          Edition,  6th Edition, 2004.
4.       Electronic Circuit Analysis and Design – Donald A. Neaman, McGraw Hill  


LECTURE  NOTES :




ASSIGNMENT - I (Theory) :

1. a. Draw the small signal High Frequency Common Emitter Model of a Transistor.
    b. Explain about all High Frequency parameters used in the model
    c. What is the order of magnitude of each parameter of the model.

2. Derive the expression for the Common Emitter short circuit current gain, Ai as a function of frequency.

3. Define  f_∞  and  f_β.  Also derive the relation between them.

4. Derive the expression for current gain and upper 3dB frequency of a Common Emitter stage with a  resistive load R_L. Assume the output time constant is small compared to the input time constant.

5. In terms of what four independent parameters, the High Frequency response of a Common Emitter stage is obtained and give the required formula.

6. Draw the small signal equivalent model for an Emitter Follower stage at High Frequencies.


ASSIGNMENT - II (Problems) :



Previous JNTU Questions :

1. From the hybrid- π   equivalent circuit of a BJT at high frequencies derive expressions for input feedback conductances and transconductance in terms of its low frequency h-parameters.

2. Obtain  the expressions for the voltage gain in the low frequency, medium frequency and high frequency ranges in the case of single stage amplifier.

3. Derive the expressions for hybrid Π conductance, gce, and gbb’ of a transistor.

4. Explain how hybrid Π parameters, gm and gce vary with Ic, Vce and temperature.

5.  Compute the overall lower cut-off frequency of an identical two stage cascade of amplifiers with individual lower cut-off frequency given as 432 Hz.









Previous GATE Questions :