0
\$\begingroup\$

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

\$\endgroup\$
  • 2
    \$\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
  • 1
    \$\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
  • 1
    \$\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

Your Answer

By clicking "Post Your Answer", you acknowledge that you have read our updated terms of service, privacy policy and cookie policy, and that your continued use of the website is subject to these policies.

Browse other questions tagged or ask your own question.