Help with detail on a schematic

[si2030]

Hi all,

Really simple question here.

I was wondering what the combination of two transistors next to the 10k resistor on the left of the diagram was... is it an SCR?

Seems that its drawn slightly wrong for an SCR... I am not sure of this though..

Could you also tell me how it works with this component.

View attachment 61402

Kind regards

Simon

 

[Nigel Goodwin]

It's a darlington.

 

[ronsimpson]

It is a Darlington transistor. The two transistors act as one with very high current gain.
https://en.wikipedia.org/wiki/Darlington_transistor

 

[ronv]

Also a very clever circuit.