I designed a circuit that is similar to the circuit on the picture below. The main difference in my design is that I am using a 3V battery and more LEDs.

enter image description here

I am using UNPOLARISED capacitors because I am aware of the oscillating voltages on the two capacitors. I also manufactured the PCB and it works like a charm.

Because unpolarised capacitors are large, expensive and I found only THT (I want SMD), I am interested in using ELECTROLYTIC POLARISED capacitors - and assuming that it is not dangerous since it is a low voltage circuit (3V battery is used, so the reverse voltage on the cap should be max around 1V).

I have already tried the circuit with polarised electrolytic capacitors (specifications 330uF, 16V) and it works just fine, and the capacitors are cold, so it seems safe. But I would like a comment from more experience guys before I make 20 PCBs and than realize that after 5 days the capacitors cause a fire or something...


  • \$\begingroup\$ They won't cause a fire, not with 100k in series with the tiny negative voltage that's the difference between Vbe and Vce(sat), for the brief moment that they're actually reversed. \$\endgroup\$ – Neil_UK Dec 10 '17 at 14:14
  • 1
    \$\begingroup\$ Polarised capacitors can have an reverse voltage on them; this value is limited by its properties. \$\endgroup\$ – Daniel Tork Dec 10 '17 at 17:05

The is okay to do, however a higher voltage rating on the capacitors is better, best not to substitute 6.3V caps.

The reverse voltage in your circuit is limited to a diode drop minus Vce(sat) which is acceptable for a conventional 16V aluminum electrolytic capacitor.


Your Answer

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

Not the answer you're looking for? Browse other questions tagged or ask your own question.