_______________________________________________________________________ Special Devices
Figure 3-47. JFET Operation With Zero Gate Bias
Figure 3-48. JFET With Reverse Bias
3-80. The application of a large enough negative voltage to the gate will cause the
depletion region to become so large that conduction of current through the bar stops
altogether. The voltage required to reduce drain current (ID) to zero is called "pinch-off"
voltage and is comparable to "cut-off" voltage in a vacuum tube. In Figure 3-48, the
negative 1 volt applied, although not large enough to completely stop conduction, has
caused the drain current to decrease markedly (from 10 milliamperes under zero gate bias
conditions to 5 milliamperes). Calculation shows that the 1-volt gate bias has also
23 June 2005
TC 9-62
3-29
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