[Amps] grounded-gate power MOSFET

[Tomm Aldridge]

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 at 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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