Why does the Darlington pair have a higher input resistance?
On July 7, in one of our discussions , LvW asked me an interesting question about the famous Darlington pair: "By the way: Some days ago I stumbled over the question: What are the advantages/disadvantages of the Darlington-pair? Do you have a short answer?" It was an exact hit because this circuit was one of my favorite circuit solutions. I immediately replied: "I have also thought a lot about the Darlington pair... I have even found an interesting phenomenon in its operation - the first transistor introduces negative feedback between the collector and the base of the second transistor. That is why, its collector voltage cannot be below 0.7 V (disadvantage)." A big advantage of this 2-transistor circuit is that it behaves like a three-pin transistor (collector, base, emitter). This allows ordinary transistors to be replaced by Darlington "transistors" (TIP) and v.v. I have often seen my son do it during car repairs... But the warm summer came, we went on...