Peak Atlas DCA Pro User Guide June 2019 – Rev 1.7
Page 23
Depletion Mode MOSFETs
The fairly rare Depletion Mode MOSFET is very similar to
the conventional Junction FET (JFET) except that the gate
terminal is insulated from the other two terminals. The input
resistance of these devices can typically be greater than 1000MΩ for negative
and positive gate-source voltages.
Depletion Mode devices are
characterised by the gate-source voltage
required to control the drain-source
current.
Modern Depletion Mode devices are
generally only available in N-Channel
varieties and will conduct some current
between its drain and source terminals
even with a zero voltage applied across
the gate and the source. The device can
only be turned completely off by taking
its gate significantly more negative than
its source terminal, say –5V. It is this
characteristic that makes them so similar
to conventional JFETs.
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