Giving the following schematic: What is purpose of R1 and the diodes ? enter image description here

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    \$\begingroup\$ Not enough context. Post the surrounding circuit, or where you got the schematic from? It looks to me like \$R_1\$, \$R_2\$ and the associated diode are there to speed up turning off \$T_2\$. The diode on the right is either intrinsic (if it's a monolithic Darlington pair) or it's there on purpose because the expected use has the collector voltage falling below the emitter voltage. \$\endgroup\$ – TimWescott Dec 10 '18 at 16:25
  • \$\begingroup\$ That's the whole circuit. I found it as a "better design of a darlington pair". \$\endgroup\$ – Baciu Vlad-Eusebiu Dec 10 '18 at 16:27
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    \$\begingroup\$ R1 and (R2 + diode) are here to speed up Cbe capacitor discharging time also they make sure that the leakage current does not turn-ON the Darlington. \$\endgroup\$ – G36 Dec 10 '18 at 16:29
  • \$\begingroup\$ But I suspect that this left diode should be connected between B and E terminals. \$\endgroup\$ – G36 Dec 10 '18 at 16:33
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    \$\begingroup\$ The left diode speeds up turning off the 2nd transistor when the B terminal is grounded. \$\endgroup\$ – Andy aka Dec 10 '18 at 16:34

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