UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - FET amplifier information biasing voltage and circuits etc

G0HZU_JMR · 4th Dec 2022, 4:02 pm

The 2N3819, MPF102, BF245, BF256 and 2N4416(A) are all process 50 JFETs. One classic way to get around the spread in parameters for process 50 JFETs is to buy either the 2N5484, 2N5485 or 2N5486 as these are all process 50 but they are graded across the range of process 50. The 2N5484 has the lowest Idss and 2N5486 has the highest.

It's difficult to find the 2N5484, 2N5485 or 2N5486 today though. They are sometimes available in SMD. The BF256 is/was available in A, B and C grades.

I think the BF256B version can still be purchased in TO-92 as there was a recent manufacturing re-run of these parts by Onsemi. Farnell have them for 38p each and have 17,000 in stock with more to follow. The Idss range for the BF256B is typically 6mA to 13mA. I think process 50 JFETs can have an Idss range from 1 to 20mA.

4th Dec 2022, 4:02 pm	#8
G0HZU_JMR Dekatron Join Date: Sep 2010 Location: Cheltenham, Gloucestershire, UK. Posts: 3,077	Re: FET amplifier information biasing voltage and circuits etc The 2N3819, MPF102, BF245, BF256 and 2N4416(A) are all process 50 JFETs. One classic way to get around the spread in parameters for process 50 JFETs is to buy either the 2N5484, 2N5485 or 2N5486 as these are all process 50 but they are graded across the range of process 50. The 2N5484 has the lowest Idss and 2N5486 has the highest. It's difficult to find the 2N5484, 2N5485 or 2N5486 today though. They are sometimes available in SMD. The BF256 is/was available in A, B and C grades. I think the BF256B version can still be purchased in TO-92 as there was a recent manufacturing re-run of these parts by Onsemi. Farnell have them for 38p each and have 17,000 in stock with more to follow. The Idss range for the BF256B is typically 6mA to 13mA. I think process 50 JFETs can have an Idss range from 1 to 20mA. __________________ Regards, Jeremy G0HZU