I managed to get a batch of NOS BF471 (PH97) for using as VAS. However just observed that their marking are different from what I found on the net/ebay/aliexpressi. Attached here is mine. Any one if they are fake or genuie?
Also the datasheet does not provide much details. Is the 10ma at +/-42V a good operating point for common emitter VAS?
Thank you in advance.
Also the datasheet does not provide much details. Is the 10ma at +/-42V a good operating point for common emitter VAS?
Thank you in advance.
Attachments
The VAS bias level is dependent on your amplifier design but virtually all larger amplifier designs here, rely on obsolete CRT television video transistors like this one, for their high voltage linearity. Consequently, it's unlikely you'll find any datasheet recommendations for audio use. The bias is required to ensure class A operation throughout the specified power range and texts such as Self's discuss bias currents. As a generalisation, 6-10mA should be adequate in generic designs using a complementary current source transistor. Other designs may call for different bias.
Your part's moulding and leadframe look genuine to me if the colours are light grey with silver ink. The only doubts I have are that the marking is stencilled and appears dark in your pic, where originals from several batches and types that I have are plain, light coloured and the batch is simply Pxxx, not PHxx. Manufacturing probably occurred in a few locations and such details may have varied between plants so this does not mean it's fake.
Consider buying genuine KSC3503/A1381 from Fairchild distributors, for this type of part, rather than being scalped for NOS parts where the are no real guarantees. On-Semi has a new range of suitable parts developed from their Sanyo lineup that could be interesting too.
Your part's moulding and leadframe look genuine to me if the colours are light grey with silver ink. The only doubts I have are that the marking is stencilled and appears dark in your pic, where originals from several batches and types that I have are plain, light coloured and the batch is simply Pxxx, not PHxx. Manufacturing probably occurred in a few locations and such details may have varied between plants so this does not mean it's fake.
Consider buying genuine KSC3503/A1381 from Fairchild distributors, for this type of part, rather than being scalped for NOS parts where the are no real guarantees. On-Semi has a new range of suitable parts developed from their Sanyo lineup that could be interesting too.
Thanks much Ian. I do appreciate for your response.
Agreed.
PS, I try collecting of good rare BJT (as well as tubes, at the right price) since through-holes BJT for audio TR seems getting fewer in choices.
Thank you.
The datasheet just say the min Hfe is 50. I took a sample of 20s and their Hfe are mostly ~120 ( a few are ~100).
http://mht.mht.bme.hu/~beged/elakszim/BF469_471_CNV_2.pdf
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