0
\$\begingroup\$

I’m trying to wrap my head around the emitter follower.

I’m currently using it to simulate a ~12V AC coming from a intercom ringer (about 700Hz).

schematic

simulate this circuit – Schematic created using CircuitLab

My input is a function generator and I would like my output to drive quite a bit of current. Right now the best I could do is drive a few mA but in the process I’m setting my \$R_E\$ on fire. Is there a way to improve the efficiency of this circuit? Or I’m better off using another buffer?

\$\endgroup\$
8
  • 1
    \$\begingroup\$ This circuit will not work as needed - use standard (two transistors) class a / ab amplifier \$\endgroup\$ – fifi_22 Nov 14 '20 at 20:46
  • 2
    \$\begingroup\$ That's what a Class A amplifier does. Search "Class B" or "Class AB Amplifier" designs. \$\endgroup\$ – user_1818839 Nov 14 '20 at 20:47
  • 1
    \$\begingroup\$ That \$R_E\$ just "pisses away" as much current as it can deliver to the output. What you need is an \$R_E\$ that varies its value depending on how much current is needed at the output. That's a job for another transistor. Like a class B (or AB) output stage. \$\endgroup\$ – Bimpelrekkie Nov 14 '20 at 21:32
  • 1
    \$\begingroup\$ So the answer to my question is to add a second transistor? \$\endgroup\$ – gurghet Nov 14 '20 at 23:48
  • 2
    \$\begingroup\$ @gurghet At least one. And a few other parts, too. \$\endgroup\$ – jonk Nov 15 '20 at 6:59

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Browse other questions tagged or ask your own question.