AN-6610 Datasheet, PDF (1/3 Pages) Fairchild Semiconductor – JFET Curve Tracer

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AN-6610
JFET Curve Tracer
Junction field-effect transistors (JFETs), unlike bipolar
transistors, do not easily lend themselves to analytic
solutions of bias networks. By their very nature, JFETs are
voltage controlled devices. Gate to source voltage (control
voltage V_GS) variations of several volts can exist within a
given part type at the same operating conditions, causing the
problem. Multiple suppliers and inadequate, or non-existent,
data sheet curves compound the problem further, requiring
data from the suppliers or the use of a curve tracer.
Figure 2 shows a simple curve tracer that can be used with
any oscilloscope, and can be built using a quad op amp and
a handful of parts. The circuit displays drain current versus
gate voltage for both P and N-channel JFETs at a constant
drain voltage.
Figure 1. Typical N-Channel JFET Transfer Curve
© 1977 Fairchild Semiconductor Corporation
Rev. 1.0 • 7/10/15
Figure 2. FET Curve Tracer
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