Wednesday, October 29, 2014

GATE Practice Problems on JFET (Junction Field Effect Transistor)

1.       An N-channel JFET has VP = -4 volts and IDSS = 10 mA.
a.       Find the minimum VDS for the device to operate in pinch-off, when VGS = -2 volts.
b.      Find the drain current for VGS = -2 volts, when VDS is 3 volts and 5 volts.

2.       The JFET in the circuit has VP = - 3 volts, IDSS = 9 mA. Find the values of all resistors so that VG = 5 volts, ID = 4 mA and VD = 11 volts. Design for 0.05 mA in the voltage divider.



3.       An N-channel silicon JFET has a donor concentration of 2 x 1021 /m3 and a channel width of 4 ยตm.
a.       Find the pinch off voltage, VP
b.      Find the saturation voltage, VDSsat, if VGS is  – 2 volts.



4.       The Q-point of a JFET in a source self-bias arrangement is chosen at VGS = - 1.5 volts and ID = 5 mA. Find the value of the resistance RS.



5.       An N-channel JFET has IDSS = 12 mA and the Transconductance of 4mA/V when VGS = 0 volts.
a.       Find the pinch off voltage, VP
b.      Find the drain current when VGS = - 2 volts.


6.       An N-channel JFET has pinch off voltage of – 4.5 volts and IDSS = 9 mA.
a.       At what value of VGS in the pinch off region will ID equal to 3 mA?
b.      What is the value of VDS(sat), when ID = 3 mA?




7.       For the given JFET, IDSS = 10 mA and VP = - 4 volts. Find the quiescent values of ID and VDS, when VGS = - 1.5 volts. Assume that JFET is biased in pinch off region.
 



8.       For the circuit shown, find the Q-point, when VGS = - 3 volts.
 



9.       For the P-channel JFET shown, find the Q-point if IDSS = 18 mA and VP = 5 volts.
 



10.   An N-channel JFET has IDSS = 16 mA and VP = - 6 volts. Calculate the drain current and VDS(sat) when VGS = - 4 volts.



11.   A P-channel JFET has a pinch off voltage of 8 volts. At what value of VGS does VDS(sat) = - 3 volts?


12.   An N-channel JFET has pinch off voltage of – 5.8 volts and IDSS = 15 mA. Find the value of ID when VGS is 0 volts, - 2 volts and – 6.5 volts.



13.   An N-channel JFET having a pinch off voltage of – 3.5 volts has a saturation current of 2.3 mA when VGS = - 1 volt. What is its saturation current when VGS = 0 volts and -2 volts.



14.   A P-channel JFET has a pinch off voltage of 6 volts and IDSS = 18 mA. At what value of VGS in the pinch off region will ID equal 6 mA? What is the value of VDS at pinch off point?



15.   The JFET shown has IDSS = 14 mA and VP = - 5 volts. Determine the Q-point for 
a.       VGS = - 3.6 volts
b.      VGS = - 3 volts
c.       VGS = - 1.7 volts




16.   Find the Q-point of the JFET shown, if IDSS = 6 mA and VP = - 3 volts.
 




17.   Determine the values of ID,VGS and VDS for the JFET shown, if IDSS = 25 mA and VP = 8 volts.






18.   Determine the values of ID, VGS and VDS of the JFET circuit shown, if IDSS = 2.42 mA and VP = - 4 volts.






19.   Find the values of ID and VDS of the N-channel JFET shown, if IDSS = 12 mA and VP = - 5 volts.








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