Re: The Venerable 741

On 11/4/24 00:54, john larkin wrote:

On Sun, 3 Nov 2024 23:17:55 +0100, Jeroen Belleman
<jeroen@nospam.please> wrote:
 

On 11/3/24 23:10, Jeroen Belleman wrote:

On 11/3/24 19:07, Cursitor Doom wrote:

It's been around an awfully long time and there are far better
alternatives out there. But is there still a case for using them in
certain niche applications in 2024?

>
I've used them in power supply regulators exposed to radiation.
Being old designs and all-NPN, they're pretty rad-hard.
>
Jeroen Belleman

>
Blimey, I just checked: It isn't all-NPN! Fortunately
for me, it still kept working under irradiation...
>
Jeroen Belleman

 The early integrated PNPs had betas in the single digits, so a bit of
radiation poisoning was no big deal.
 

Non, au contraire, in bipolar transistors, irradiation tends to
reduce beta at low current. If it's already low to begin with,
a bit of irradiation will soon make it drop to useless values,
and the chip stops working.
My typical example used to be the LM317 as compared to the LM337.
The latter has (had?) a large lateral PNP which did not survive
for long (<50Gy). The LM317 just kept going (>1kGy).
However, chip design changes that do not affect operation under
normal circumstances can radically change radiation resistance.
Jeroen Belleman