BF200 Transistor alternative

[k7420]

I'm having hard time finding this transistor in my local market,, I want a replacement of this transistor. Alternatively what transistor can be used beside BF200?

 

[MikeMl]

Polish data sheet. I,m not surprised it is hard to find.

 

[Roff]

MPSH10 might work, but you may not be able to get that in Karachi either. 2N918 used to be a common RF transistor. The junction capacitances are considerably higher than those of BF200, so it might not work, even if you could get it.

 

[k7420]

Bc547

BC547 is commonly available here, and also is 2n2222... What do you think about replacing BF200 to any of these transistors?

 

[Roff]

BC547 is commonly available here, and also is 2n2222... What do you think about replacing BF200 to any of these transistors?

According to the datasheet, BF200 is an RF transistor with high fT and very low junction capacitances. If it is used in an RF application, you probably cannot substitute BC547 or 2N2222, or 2N3904, or any other general purpose transistor.

 

[k7420]

Okay leaving BF200 aside.

Is BF494 equivalent to 2n3904, 2n2222, bc547?

 

[Roff]

Okay leaving BF200 aside.

Is BF494 equivalent to 2n3904, 2n2222, bc547?

No. You need to learn to read datasheets.

 

[colin55]

What frequency is the circuit?

 

[k7420]

100MHz.. Im trying to use it for an fm transmitter....

 

[k7420]

I don't know how to read it,, BF494 is a 260MHz transistor and 2n2222 is a 300MHz transistor,, by using different oscillator capacitors and coils, we can get desired frequency... all these transistors are low powered....

 

[colin55]

Are you using it in the oscillator or buffer (output) stage?
Anything will work in the oscillator stage and something slightly better is needed if used as an output.

 

[audioguru]

I use a 2N3904 transistor as the oscillator and another 2N3904 transistor as the RF amplifier in my FM transmitter and it works perfectly.

 

[k7420]

colin55
Are you using it in the oscillator or buffer (output) stage?
Anything will work in the oscillator stage and something slightly better is needed if used as an output.

BF494 is in oscillator stage and BF200 is in pre-amplifier stage in transmitter. let me post the schematic....

 

[colin55]

What you have to do is get a LED Power Meter from Talking Electronics website and put it on the base of the transistor in the pre-amp section and then the collector of the pre-amp stage and see if there is any gain. Remove the other output stages during this test.

 

[k7420]

Okay thank you colin, I have to build that power meter, that's a must have in RF tool