Re: [Amps] grounded-gate power MOSFET

[Tomm Aldridge <KD7QAE@ARRL.NET>]

Yes, except the 15V supply is established with respect to the source. 
As I said, I have built the version with a bipolar on the top which was 
emitter switched by the FET on the bottom of the pair.  W/ proportional 
drive on teh bipolar, it was fast and efficient.

Angel Vilaseca wrote:

> 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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