GATE Practice Problems on JFET (Junction Field Effect Transistor)

1. An N-channel JFET has V_P = -4 volts and I_DSS = 10 mA.

a. Find the minimum V_DS for the device to operate in pinch-off, when V_GS = -2 volts.

b. Find the drain current for V_GS = -2 volts, when V_DS is 3 volts and 5 volts.

2. The JFET in the circuit has V_P = - 3 volts, I_DSS = 9 mA. Find the values of all resistors so that V_G = 5 volts, I_D = 4 mA and V_D = 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 µm.

a. Find the pinch off voltage, V_P

b. Find the saturation voltage, V_DSsat, if V_GS is – 2 volts.

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

5. An N-channel JFET has I_DSS = 12 mA and the Transconductance of 4mA/V when V_GS = 0 volts.

a. Find the pinch off voltage, V_P

b. Find the drain current when V_GS = - 2 volts.

6. An N-channel JFET has pinch off voltage of – 4.5 volts and I_DSS = 9 mA.

a. At what value of V_GS in the pinch off region will I_D equal to 3 mA?

b. What is the value of V_DS(sat), when I_D = 3 mA?

7. For the given JFET, I_DSS = 10 mA and V_P = - 4 volts. Find the quiescent values of I_D and V_DS, when V_GS = - 1.5 volts. Assume that JFET is biased in pinch off region.

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

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

10. An N-channel JFET has I_DSS = 16 mA and V_P = - 6 volts. Calculate the drain current and V_DS(sat) when V_GS = - 4 volts.

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

12. An N-channel JFET has pinch off voltage of – 5.8 volts and I_DSS = 15 mA. Find the value of I_D when V_GS 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 V_GS = - 1 volt. What is its saturation current when V_GS = 0 volts and -2 volts.

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

15. The JFET shown has I_DSS = 14 mA and V_P = - 5 volts. Determine the Q-point for