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Joerg
Guest
Sun Feb 07, 2010 6:14 pm
Paul Keinanen wrote:
Quote:
On Fri, 05 Feb 2010 23:28:40 GMT, Jan Panteltje
pNaonStpealmtje_at_yahoo.com> wrote:
Even more interesting is the maximum speed it can do
I am not talking about 100GHz.
What exactly does cut off frequency mean for a FET ?
In bipolars the current gain drops below 1 at fT but you still can get
some usable power gain in common base configuration at higher
frequencies.
Common gate is even done with FETs. A professor at our university once
proclaimed that would be stupid. Until I showed him the schematic of my
amp and then that of a commercial transceiver ...
Quote:
Before the invention of real microwave tubes (such as klystrons,
magnetrons TWTs etc.) much of the UHF/microwave amplification was done
my grounded grid tubes.
Still is. The nice advantage of that is that you don't have to burn off
the drive power in the form of heat.
--
Regards, Joerg
http://www.analogconsultants.com/
"gmail" domain blocked because of excessive spam.
Use another domain or send PM.
Jamie
Guest
Sun Feb 07, 2010 6:43 pm
Joerg wrote:
Quote:
Paul Keinanen wrote:
On Fri, 05 Feb 2010 23:28:40 GMT, Jan Panteltje
pNaonStpealmtje_at_yahoo.com> wrote:
Even more interesting is the maximum speed it can do
I am not talking about 100GHz.
What exactly does cut off frequency mean for a FET ?
In bipolars the current gain drops below 1 at fT but you still can get
some usable power gain in common base configuration at higher
frequencies.
Common gate is even done with FETs. A professor at our university once
proclaimed that would be stupid. Until I showed him the schematic of my
amp and then that of a commercial transceiver ...
JFETS I presume?
Joerg
Guest
Sun Feb 07, 2010 6:43 pm
Jamie wrote:
Quote:
Joerg wrote:
Paul Keinanen wrote:
On Fri, 05 Feb 2010 23:28:40 GMT, Jan Panteltje
pNaonStpealmtje_at_yahoo.com> wrote:
Even more interesting is the maximum speed it can do
I am not talking about 100GHz.
What exactly does cut off frequency mean for a FET ?
In bipolars the current gain drops below 1 at fT but you still can get
some usable power gain in common base configuration at higher
frequencies.
Common gate is even done with FETs. A professor at our university once
proclaimed that would be stupid. Until I showed him the schematic of
my amp and then that of a commercial transceiver ...
JFETS I presume?
Sometimes. But the one I dealt with on my very first job was a MOSFET.
--
Regards, Joerg
http://www.analogconsultants.com/
"gmail" domain blocked because of excessive spam.
Use another domain or send PM.
Fred Abse
Guest
Mon Feb 08, 2010 10:09 am
On Sun, 07 Feb 2010 09:14:24 -0800, Joerg wrote:
Quote:
Common gate is even done with FETs. A professor at our university once
proclaimed that would be stupid.
Why so? Hadn't he heard of grounded grid triodes?
--
"Electricity is of two kinds, positive and negative. The difference
is, I presume, that one comes a little more expensive, but is more
durable; the other is a cheaper thing, but the moths get into it."
(Stephen Leacock)
Joerg
Guest
Mon Feb 08, 2010 6:17 pm
Fred Abse wrote:
Quote:
On Sun, 07 Feb 2010 09:14:24 -0800, Joerg wrote:
Common gate is even done with FETs. A professor at our university once
proclaimed that would be stupid.
Why so? Hadn't he heard of grounded grid triodes?
Definitely not because his eye popped open when I showed him a schematic
of a grounded grid RF power amp. I tended to build mine grounded cathode
but only because I didn't have enough drive power or back then as a
student not enough dough to buy the required new tubes. Or to be honest,
I didn't want to raid the beer kitty to buy those.
--
Regards, Joerg
http://www.analogconsultants.com/
"gmail" domain blocked because of excessive spam.
Use another domain or send PM.
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