JFET Active Crossover

[jackinnj]

Other alternative transistors?

2N5457 and 2N5460 (MMBF5457 and 5460) -- I was surprised that the noise isn't as bad as in the old datasheets. They are, by no means, as quiet or "gm muscular" as the original Toshiba parts. The pins are arranged differently with the Fairchild devices.

 

[merlin el mago]

Thanks, I only source SOT-23, I'm looking for TO-92.

 

[jackinnj]

There are adapters for SOT23 to TO92 sold on EBay

 

[merlin el mago]

Thanks again.

 

[EUVL]

> There are adapters for SOT23 to TO92 sold on EBay

There are quite a few for SOT23 to DIP6 or SIP3 (2.54mm pitch).
I cannot find any that is TO92 (1.27mm pitch, 5x5mm board size).
Perhaps you can post a link ?


Patrick

 

[AndrewT]

Those all look like they will fit to a PCB drilled to accept To92.

 

[EUVL]

If you can live with 7.5x10mm board size, then yes.

This is 5x5, true TO92 size :

http://www.diyaudio.com/forums/head...eadphone-amp-linear-audio-15.html#post3930254
http://www.diyaudio.com/forums/atta...h-headphone-amp-linear-audio-sot23_2_to92.jpg


Patrick

 

[merlin el mago]

What about these duals?

Printed circuit board adapters SOT23/SSOP to DIP6.
Top side is suitable for packages like single SOT23-6, SOT23-5 or SOT23-3 with a pitch of 0.95mm.
Alternatively 2 pieces of SOT23-3 can be soldered overleaf.

 

[EUVL]

Look carefully at the pin assignments, and see whether they corresponds to a TO92 JFET of your choice.


Patrick

 

[merlin el mago]

Could I use JFET, PMBF4393 Compre Transistores JFET Transistor JFET, PMBF4393,215, N-Canal, 30mA, 40V, TO-236AB, 3-Pines NXP PMBF4393,215 en RS Online y lo recibir en 24 horas. in place of PN4393?

 

[wrenchone]

Should work ok, as they're SOT-23 versions of the TO-92 part, which was the TO-92 version of the original TO-18 metal can part (2N4393). Some Ebay sellers in China offer a clamshell-type socket which could be used for testing/screening devices. One could also test them after mounting them down on an adapter board.

 

[merlin el mago]

Thanks, It's necessary to match de NJEFTs, wich Idss, other parameters to match?

First to buy the SOT23 to TO92 adaptor I want to try like the attached pic, do you think it will works?

TIA
Felipe

 

[wrenchone]

Let me know where you find a header with small enough pitch to accommodate SOT-23s as shown.

The only fets that could really use matching are the ones used for the bottom current source of the follower, and that's a matter of convenience so one can use all the same resistor for setting the bias current. You could roughly match the fets with IDSS sorting, experiment with the value of source resistor needed for a desired bias current (somewhere between 5-10 mA), and use that resistor for all the matched bottom fets.

Another alternative is to use the BSS159 depletion mode fet for the current source. The consistency of these devices right out of the bag make matching mostly unnecessary. If I recall correctly, ~200 ohms source resistor will get you about 10 mA bias current. Raising the resistor lowers the bias current. As usual, you should use a 1k stopper resistor from gate to ground to prevent oscillation.

 

[merlin el mago]

I will look for BSS159.

 

[merlin el mago]

Wich one of these two?

Transistores MOSFET y piezas para Semiconductores Discretos

 

[wrenchone]

I don't understand why that particular site lists two devices with the same part number and different current ratings. The ones I got from Digi-Key were the 0.23A rated devices, the only BSS159s listed there, and in a legitimate SOT-23 package.

 

[merlin el mago]

Thanks for help.

 

[EUVL]

See the same at Mouser :
Infineon bss159 MOSFET | Mouser

BSS159N H6327 is random Vgs.
BSS159N L6906 is pre-selected in Vgs bands.

See datasheet P.1 & Figure 11.

Idss 130mA is IMHO way too overkilled as a JFET buffer for line level.
You may also wish to consider 2SK209BL, or 2SK2145BL (dual), both available from Mouser.


Patrick

 

[merlin el mago]

I have to use BSS159 in place of PN4393 as red marked circles in your attached schematic?

 

[merlin el mago]

I have to use BSS159 in place of PN4393 as red marked circles in your attached schematic?

I guess isn't correct, I guess the new attached one is the correct?