I made my first inverter design and I got a lot of help from this website. But I want to get your suggestions before something goes wrong. Circuit output is 12V AC 72Hz square wave.

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I used NE555 as frequency generator to get 12V-0V pulse signal (72Hz). When the pulse signal is high (12V) Q3 opens and output is 12V. When the pulse signal is low (0V) Q4 opens and output is -12V.

Also I don't understand why no shortcuts happen in here?

Q5 transistor converts NE555's 0V signal to 12V signal for Q4.

Also I'm sorry if you had trouble to understand it, my English is little rusty.

  • \$\begingroup\$ Normally, "open" means a switch is not conducting and "closed" means a switch is conducting. It's not like a door. And I think by "shortcut" you mean "short circuit"? Where are you expecting a short circuit to happen? \$\endgroup\$
    – DKNguyen
    Jul 26, 2019 at 3:26
  • \$\begingroup\$ @DKNguyen an inverted door? :) \$\endgroup\$
    – Solar Mike
    Jul 26, 2019 at 3:27
  • \$\begingroup\$ @SolarMike An upside down door still behaves identically to a right side up door. Perhaps you mean an inside-out door. (Mordecai: Just ignore this, we're both just talking nonsense). \$\endgroup\$
    – DKNguyen
    Jul 26, 2019 at 3:28
  • \$\begingroup\$ @DKNguyen we can go through an open door, but electricty cannot go through an open switch ... \$\endgroup\$
    – Solar Mike
    Jul 26, 2019 at 3:35
  • \$\begingroup\$ I'm sorry for inconvenience , electrical terms changes between languages and I meant when Q3 or Q4 closed why short circuit happens but now I understand it thanks to the comments \$\endgroup\$
    – Mordecai
    Jul 26, 2019 at 3:36

1 Answer 1


This is not an answer but just to help with terminology.


simulate this circuit – Schematic created using CircuitLab

Figure 1. In switches "open" and "closed" refers to the gap between the contacts.

  • \$\begingroup\$ So if I understand it correctly : when the Q4 conducting it opens Q2 and yellow wire outputs 0V .Q1 is normally closed but Q3 not conducting so and blue wire outputs 12V ? But I don't know why Q4 effects Q2 \$\endgroup\$
    – Mordecai
    Jul 27, 2019 at 2:53

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