Off the top of my head. I may have this wrong, but this "sounds logical":

It's not that the inductance is high but that the frequency is. As
frequency rises inductance has an increasing impedance and capacitance has
decreasing impedance (as I know you know).

Capacitive reactance falls with frequency and inductive rises.
Reactance from very small inductances (in the order of 10ths to 100ths of
uH) will match the impedance of capacitors in the 100 of pF - 1's of nF
range.
eg

Z =3D 2 x Pi x f x L  so
L =3D Z/(2 Pi F)
=3D 6.97/(2 x 3.14 x 9E8) =3D~ 1.2 NANO Henry
You don't need much lead structure to get 0.001 uH.

Capacitance to balance that at 900 Mhz =3D
C =3D 1/ (2 Pi F  Z ) =3D 25 pF
Greater than 25 pF will have a Z LOWER than -j6.97 Ohms.


     Russell



On 21 March 2016 at 02:42, Jason White <whitewaterssoftwareinfo@gmail.com>
wrote:

> I was looking at the datasheet for the PD85004, a 4 watt radio frequency
> MOSFET, and I noticed something peculiar.
>
> In the datasheet [1] for this transistor the complex impedance of the gat=
e
> is specified versus frequency. According to the table 8 on page 5 of the
> datasheet the impedance of the gate is primarily inductive not capacitive=
!
> For example at 900MHz the gate impedance is specified as "2.63+j6.97".
>
> I have attached a picture of the diagram and the table. MOSFET gates are
> essentially large capacitors, so how could it present an inductive
> impedance? Would this be caused by the inductance of the leads and wire
> bonds inside of the FET?
>
> --
> Jason White
>
> --
> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist
>
>
--=20
http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist
.