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A GREAT ER M EA SU R E O F C O N F I D E N C E referred to as the operating point or quies-
cent point (q-point). The technique in this
type of testing is application of a low duty
cycle pulse (typically <1%) to the device
under test (DUT), which avoids self-heating
and carrier trapping. As shown in the left
view of Figure 1, each point on the curve is
the result of a pulse measurement made on
the DUT during the settled or flat portion of
the pulse. In practice, many pulse measure-
ments are averaged to improve the quality of
measurement results.
The second type of PIV testing is the
Dual Channel Pulse
transient or single pulse test (right view in
Figure 1). In this case, the test results are
presented as a view of the measurement
Testing Simplifies
pulse, or an average of multiple pulses. The
measured signal is plotted as the DUT's volt-
age or current versus time response, showing
RF Transistor any time-varying changes, such as the onset
of self-heating or charge trapping.
Characterization
A wide range of pulse widths can be
useful in PIV testing, depending on the
device or material type and test parameters.
For millisecond pulse widths, ordinary
source-measure units (SMUs) can be used.
However, shorter pulses (microseconds to
Pete Hulbert, Keithley Instruments, Inc. nanoseconds) are generally more effective
for avoiding self-heating and charge trapping
effects. Therefore, short-pulse PIV testing of
Device engineers and test managers are measurement. Since RF transistors are pri- RF transistors generally allows the creation
under tremendous pressure to make sure marily used in applications where non-linear of more useful models.
products get to market quickly and perform responses are the norm, such as switches and
reliably. This is especially true of RF transis- amplifiers, large signal analysis is typically Small Signal vs.
tors destined for hot communications market the goal of PIV testing. The two main test Large Signal Testing
segments. Whether the technology is based methodologies are PIV sweeps and transient A useful dichotomy in describing RF
on III-V compounds or LDMOS, RF transis- (single pulse) testing (Figure 1). By using a transistor characterization is the distinction
tor tests must accurately characterize design dual-channel pulse source-measure system, between small signal and large signal test-
and performance