The drain and gate bias voltages are set to 1.2 and -1.25 V, respectively, for a near pinch-off voltage
operating region between classes B and C.
The E-mode device features a nominal +350 mV pinch-off voltage
and corresponding [I.sub.MAX] and [I.sub.DSS] of 290 and 0.0005 mA/mm, respectively.
[I.sub.dss] is the drain saturation current at zero [V.sub.gs], [V.sub.P] represents pinch-off voltage
and GAM is the pinch-off slope parameter.
The device is an ion-implanted, gate recessed MESFET with a 0.5 [micro]m gate-length and a pinch-off voltage
of -0.8 V.
The peak reverse voltage across the gate must be taken into account if the MESFET is being biased much below pinch-off voltage
(that is if [V.sub.gg] < [V.sub.t]).
In Curtice and Ettenberg (1), this is described as a shift in pinch-off voltage
, but it could also be called a kind of sub-threshold conduction.
Since channel resistance changes sharply for gate source voltage ([V.sub.gs]) close to the pinch-off voltage
([V.sub.p]), the stability and repeatability of the transfer curve is governed mostly by [V.sub.p].
In order to describe the general findings of this work, a 900 [mu]m gate-width (four fingers with 225 [mu]m gate width per finger), -0.8 V pinch-off voltage
, 0.5 [mu]m gate-length ion-implanted GEC Marconi Materials Research Ltd.
(The DFET has a wider range between the drain supply voltage and the gate pinch-off voltage
Increasing the pinch-off voltage
or decreasing the open channel current by increasing the channel height and/or width increases the intercept point performance of the device.
These devices offer high gate-drain and gate-source breakdown voltages, near-constant transconductance with gate bias down to pinch-off voltage
and moderately high maximum channel current that enables high efficiency to be obtained.