TO-92 transistor for HF amplifier, more powerful than pn2222

[neazoi]

Hello, I am building a small QRP amplifier for HF and I was wondering if there is any common transistor more powerful than pn2222 in the same small plastic case (TO-92)?

 

[Audioguru]

A PN2222 is for "general purpose". There are transistors available in the TO-92 case designed for RF high frequencies.

 

[neazoi]

A PN2222 is for "general purpose". There are transistors available in the TO-92 case designed for RF high frequencies.

Which are they?
Same or greater power rating

 

[aProgrammer]

MPS918

(2N918 in TO-92 case)

is an example.

 

[neazoi]

MPS918
(2N918 in TO-92 case)
is an example.

MPS818 has Ic 50mA
PN2222 has Ic 600mA

I am looking for a more powerful common transistor for HF in the same case.

 

[aProgrammer]

MPS3866 is probably more powerfull

but also you should understand than (in rf)
that output power of a mps918
will be always better than a pn2222

 

[Audioguru]

A PN2222 has a maximum allowed collector current of 600mA. That is for continuous DC that has no frequency. At 100MHz its minimum current gain is only 2.5 which is not much better than a piece of wire.

 

[neazoi]

A PN2222 has a maximum allowed collector current of 600mA. That is for continuous DC that has no frequency. At 100MHz its minimum current gain is only 2.5 which is not much better than a piece of wire.

It is so wonderful to learn every day new things from this forum!
I was not aware about the frequency thing.

What is the parameter I need to look for, from the datasheets, to judge if a transistor is more powerful than another in RF?

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MPS3866 is probably more powerfull

but also you should understand than (in rf)
that output power of a mps918
will be always better than a pn2222

Is the mps3866 like the 2n3866 but in plastic package?

How about the 2n4401? I have plenty of them in the lab. For HF 1-30MHz use.

 

[Audioguru]

A 2N4401 is another "general purpose" transistor, not an RF transistor. Its typical gain-bandwidth product is 250MHz where it has no current gain like a piece of wire and at 25MHz its typical current gain is only 10. Its minimum frequency or minimum current gain is much less.

 

[dick_freebird]

I have seen some TO-92-like cases which have an itty
bitty "power tab" sticking out, presumably to help with
thermal impedance (you might even be able to solder to
a better sink). But why is TO-92 so important, while other
can and tab styles aren't considered?

You can also, I believe, find press-on heat sinks for TO-92
devices which will at least improve upon free-air heat
throw.

You want a fT which exceeds your desired forward gain
times signal frequency.

 

[neazoi]

I have seen some TO-92-like cases which have an itty
bitty "power tab" sticking out, presumably to help with
thermal impedance (you might even be able to solder to
a better sink). But why is TO-92 so important, while other
can and tab styles aren't considered?

You can also, I believe, find press-on heat sinks for TO-92
devices which will at least improve upon free-air heat
throw.

You want a fT which exceeds your desired forward gain
times signal frequency.

Thanks all for your answers.

I parallel multiple transistors (10 of them) to make a class-A 1W HF amplifier, so you can get an idea of the circuit I am working on.
Heatsinking is done by a small fan, blowing forced air to the transistors. This is lighter, smaller size and cheaper than a huge heatsink required for class-A for the heatsink-requiring packages. I have managed to make a class-A 1W HF amplifier using 10 2n4401 and 15R emitter resistors, with about 40mW input. All harmonics are -40dbc. I think it is a good setup.
I am looking for these TO-92 because they are generally cheap, 10 of them are the same cost as a big 2sc2166 (which did not gave a better performance).

What sort of Ft should I look for, for the 1-30MHz range? Should I look for an Ft in the UHF range?
Like for example the 2sc9018 Ft 700MHz min Ic 50mA???