![]() load line for the JFET amplifier shown in Fig. The parameters of JFET are IDSS = 10 mA and VGS (off) = – 5 V. If VDD = 30 V, R1 = 1 MΩ and R2 = 500 kΩ, find the value of RS. In an n-channel JFET biased by potential divider method, it is desired to set the operating point at ID = 2.5 mA and VDS = 8V. Determine ID and VGS for the JFET with voltage-divider bias in Fig. The JFET parameters are IDSS = 5 mA and VGS (off) = − 2 V. In a self-bias n-channel JFET, the operating point is to be set at ID = 1.5 mA and VDS =10 V. The voltage VD should be 6V (one-half of VDD). The JFET parameters are : IDSS = 15 mA and VGS (off) = – 8V. 6 to set up an approximate midpoint bias. Determine the value of RS required to self-bias a p-channel JFET with IDSS = 25 mA, VGS (off) = 15 V and VGS = 5V. The transfer characteristic of a JFET reveals that when VGS = – 5V, ID = 6.25 mA. Since there is no gate current, there will be no voltage drop across RG. Determine the values of VGS, ID and VDS for the circuit. 4 has values of VGS (off) = – 8V and IDSS = 16 mA. Determine the transconductance for VGS = – 4V and find drain current ID at this point. The datasheet of a JFET gives the following information: IDSS = 3 mA, VGS (off) = – 6V and gm (max) = 5000 μS. When VGS of JFET changes from –3.1 V to –3 V, the drain current changes from 1 mA to 1.3 mA. Find the resistance between gate and source. When a reverse gate voltage of 15 V is applied to a JFET, the gate current is 10−3 μA. The drain current for the circuit is given by Determine the value of drain current for the circuit shown in Fig. One of these units had a frequency cut-off of 50 mc/s with a transconductance of 1.6 ma/v when operated at 40 volts and 40 ma.Q5. It is shown that the performance of these units is in agreement with theory. A reasonable estimate of the minimum voltage is 1/2 volt and this leads to a maximum value of f of 1,000 mc/s.Ī description is given of the fabrication and performance of several field-effect transistors operating in both the constant and non-constant mobility ranges. The pinch-off voltage cannot, however, be made indefinitely small because the gate junction must be in the saturated condition. It is found that f is inversely proportional to the “pinch-off” voltage. The performance in this particular case is considered in detail and the results summarized in a design nomograph. It is concluded that a good compromise is to operate with the average channel field equal to E c. It is shown that, although both f and g m continue to increase with electric field in this range, the corresponding increase in the power dissipated is so rapid that such designs are unattractive. New theory is derived for the performance with electric fields greater than E c, where the mobility is proportional to E −1/2. This work is reviewed and it is shown that, in this range of operation, the frequency cut-off, f, and transconductance, g m, of the device increase with increasing values of electric field. Previous work on field-effect transistors considered the performance of the device when operated with electric fields in the channel below the critical field, E c, where the mobility of carriers becomes dependent on field.
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