Velleman DCA55 - Manual (Page 19)

Atlas DCA User Guide October 2007 – Rev 7
Page 19
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 current between it’s 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 it’s gate significantly more negative than
it’s source terminal, say –10V. It is this characteristic that makes them so
similar to conventional JFETs.
Pressing scroll-off will cause the
pinout screen to be displayed.
Depletion mode
N-Ch MOSFET
RED GREEN BLUE
Drn Gate Srce