4
$\begingroup$

I'm planning to build an FM radio receiver using the instructions on http://www.instructables.com/id/Build-your-own-Crude-FM-Radio/

The schematic uses a BF199 transistor which is marked "obsolete" by some component suppliers. What would be a current and widely available equivalent?

I tried to search at my preferred shop, https://www.rs-online.com using the following properties:

  • Si NPN RF Transistor
  • Vcb max 40V
  • hFE min 38
  • ft 1100 MHz
  • Pc 350 mW

And did not find anything suitable.

The original data sheet is here: https://www.mouser.com/ds/2/308/BF199-1118776.pdf

$\endgroup$
2
$\begingroup$

This is not a terribly critical application, and there are many transistors that would work. If you have some NPN transistors on hand, try those. It may work anyway, with some reduction in gain. If you'd like to buy new transistors, I'd look for something with a high gain bandwidth product.

$\endgroup$
  • $\begingroup$ Phil Frost I think you're wront at'll, all transistor're designed for a specific target. Overall, about rf, medical instrumentacion, space application, etc. There's not a simple answer. $\endgroup$ – user14522 Mar 23 at 4:43
  • $\begingroup$ @user14522 It is not the case that all transistors are designed for a specific application. $\endgroup$ – Mike Waters Mar 24 at 0:50
  • 2
    $\begingroup$ Yes. That’s why there are “general purpose” transistors $\endgroup$ – Scott Earle Mar 24 at 5:00
2
$\begingroup$

Looks like a 2N5109 will work. Datasheet here.

$\endgroup$
  • $\begingroup$ You'd get more points if you found one that met (or exceeded) the original specifications, and was in a TO-92 package ;) $\endgroup$ – Scott Earle Mar 8 '18 at 2:13
  • $\begingroup$ @ScottEarle So are you saying the 2N5109 didn't meet the original specs? I thought that it did. It comes in different packages, but I always buy it in the TO-39 metal package so that I can heatsink it for some of my applications. $\endgroup$ – Mike Waters Mar 23 at 23:39
  • 1
    $\begingroup$ It looks like it meets (or exceeds) the specs, but being a different case style means you can’t just drop a replacement in and not have to worry about which pin is which. Someone with less electronics experience would probably be more worried about getting the pins the wrong way round than whether the Hfe was high enough (for example) $\endgroup$ – Scott Earle Mar 23 at 23:54
  • $\begingroup$ @ScottEarle Okay then, can you answer the question with a better transistor? :-) $\endgroup$ – Mike Waters Mar 24 at 20:15
1
$\begingroup$

When faced with a question like this, I find it easiest to use the selection "filters" at the web sites of the major distributors. My favorites are DigiKey, Mouser and Arrow, but there are others and your region may have different suppliers.

Using the Mouser web site, I was able to find six (6) part numbers with $f_t$ between 600MHz and 1200MHz, priced between 80 cents and 5 dollars.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.