transistor alternatives for 990 op amp

[saint gillis]

Hi, it's almost impossible to find pn2484 at a resonable price (in Europe),
  Have you found them anywhere?

  If not is there an alternative, replacement? Even if not pin to pin...

Thank you

 

[saint gillis]

http://www.whistlerockaudio.com/cart/documents/ML918/ML918%20Kit%20Manual.pdf

  Looks like it has been used as a 2N2484 replacement by Jensen.. they are easier to find

The datasheets are not exactly the same
http://www.fairchildsemi.com/ds/PN/PN2484.pdf
http://www.centralsemi.com/PDFs/products/2n2484.pdf

 

[JohnRoberts]

The metal 2484 will dissipate more power than the plastic device.

The metal can is generally connected to the collector so you might need to be careful that it doesn't touch something it shouldn't.

The document listed does not show a schematic so I can't tell what specs if any are important.

JR

 

[saint gillis]

Here is the 918 doc :
http://www.sg-acoustics.ch/analogue_audio/discrete_opamps/pdf/918_documentation.pdf

 

[dmp]

The metal 2484

Probably won't fit in the small PCBs, if you're going for the 2520 footprint. I would stick with the plastic.
Since they are both used in the circuit to simply set quiescent current, swapping a different transistor should be pretty easy, I think. Just look for the same power handling and pinout. 
http://www.johnhardyco.com/pdf/990.pdf

 

[saint gillis]

It is for an experimental project using a pcb of its own footprint, so pinout don't matter...
  Do you think it is better to use pnp/npn pairs like bc560/bc550 or should I better keep PN4250A (I have some) and use a substitute for PN2484 (like BC550) ?

 

[saint gillis]

http://www.technicalaudio.com/pdf/Jensen_Transformers/Jensen_OpAmps_990_and_related/Jensen_JE-990_opamp_JAES_reprint_1980.pdf

From Jensen papers :

The transistors for Q5, type 2N4250A or PN4250A, must have an input capacitance Cib lower than the Jedec specification in order to achieve the short response time which favors good phase margin, stability, and transient response. Fairchild and National Semiconductor have been tested and used; other types with the same part number cannot be safely substituted without analysis of the resulting response time and phase margin.

Also for the NPNs it is specified :

Q4.7 2N2484.PN2484 npn transistor National Semiconductor or Fairchild

 

[dmp]

pnp/npn pairs l

I don't think they are used as pairs electronically...
I would use 4250s if you have them

 

[saint gillis]

I found easiely 4250s on mouser, but no 2484, I m tempted to use BC550 instead...

 

[JohnRoberts]

Pin out looks different but part close...  One way to find out for sure.  ;D

JR

 

[gar381]

I have used BC550s  for pn2484s before.. Just spin it 180 deg. to get the right pinout.

the 2n5088 has the same pinout as the pn2484 and will work fine as a replacement
in some circuits but has lower max voltage ratings.

As JR says.. One way to find out for sure. ;D 

GARY