UJTs PUJTs ?

[Terry Bites]

Does anyone design in unijuctions any more or do they just exist because people still buy them by accident?

They were obsolete when I started out in the early 80s.
Other than 70s dimmer switches and hoplesly drifty timers what purpose do the serve now?
Any one got a rational application?2

[Xena E]

Design no,  however a couple of built to order legacy products using them for phase angle triggering of thyrisor/triac industrial power controllers, one for a vibratory conveying system, the other a magnetic reluctance VSD.

Both units use the obsolete 2N2646 of which the remaining stock is watched carefully, it's not that they can't be re-engineered, I just don't think they will: at least not for the VSD anyhow

I didn't think anyone actually still made them?

Regards,
X.

[T3sl4co1l]

Even PUTs are obsolete (or getting there) now; most things they were used for, have been simplified (e.g. dimmers with DIACs) or integrated (timers; ASICs with osc/counter/MCU/etc.; regulators/controllers with built-in fault circuitry; etc.).

Tim

[PCB.Wiz]

Does anyone design in unijuctions any more or do they just exist because people still buy them by accident?

They were obsolete when I started out in the early 80s.
Other than 70s dimmer switches and hoplesly drifty timers what purpose do the serve now?
Any one got a rational application?2

Variant parts like DIAC and break over diodes are still made in volumes, but 3 or 4 terminal parts are very rare.
You can buy a NPN+PNP pair (possibly with inbuilt resistors) in a SOT353 package and make your own, should you really need to.

[coppercone2]

I feel like we are not smart enough to figure out how to use them right