You mean something like this?
See schematic attached
73 de Angel Vilaseca HB9SLV
Tomm Aldridge wrote:
> I have designed and built cascode hybrids made from a HV bipolar and a
> LV IR MOSFET device. Ther work very well. No reason a FET - FET should
> not work as well or better. It would be imperative to keep the gate to
> source voltage within safe operating limits of course.
>
> Radio WC6W wrote:
>
> > On Fri, 14 May 2004 11:23:42 +0200 Angel Vilaseca <avilaseca@bluewin.ch>
> > writes:
> >
> >>Hi,
> >>
> >
> > <snip>
> >
> >>My question is: Could a gate-grounded circuit help with the
> >>power-MOSFET
> >>input matching problem?
> >>
> >>More generally: Has someone already tried to build a grounded-gate
> >>power MOSFET amplifier?
> >>
> >>
> >>
> >>Angel Vilaseca HB9SLV
> >>
> >>
> >
> >
> > Hi Angel,
> > You would still have the horrific input capacitance in GG and an even
> > lower impedance to drive.
> >
> > I've been contemplating a cascode connection to alleviate the input
> > capacitance using a low voltage (25V) FET for the input device connected
> > to a 500V FET, with the gate biased to 15V or so, to complete the
> > cascode.
> >
> > The low voltage input FET has 1/10 or so of the capacitance of the HV
> > part. If the HV FET's have a 200V Drain supply the output impedance will
> > be in the vicinity of 50 ohms which will be easier to match to the load
> > than a typical transistor circuit.
> >
> > I've seen cascodes of similar design used for driving CRT's and other
> > things but, never for RF power. There may, or may not, be a reason why
> > not... :-)
> >
> > 73 & Good morning,
> > Marv WC6W
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> > *
> >
> >
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