Amplifier circuit for door phone 3v3


Mainly, I am looking any speaker amplifier circuit for 3v3 power supply. In nutcell, I try found good, universal and long live amplifier circuit as traditional LM386.

Typically I use 12 … 48V power supplies, and now must found somethn for 3v3.

Door phone standard is EN50486. Exactly I try found somethin for call signal. Standard say: “Acoustic call signal must be 73 dB or more. Measuring environment, signal source installed to rigid material and measuring distance 500 mm. Maximum pressure not exceed 120 dB.”

Of course there is many “limitations” and “but”, but mainly start point is quite easy. It “but” etc “is there any plastic box” “is there any limit voice out” etc etc, but: More than 73 dB. After some tests look normal mobile phone can make signal which exceed this 73 dB, so maybe this is possible. Also this “120 dB”, it is not problem— it is much easier limit. “Enough volume” is bigger problem.


  • 3v3 power supply
  • any loudspeaker. “Normal” loudspeakers also acceptable, eg. 30 mm loudspeaker. 4 ohm, 8 ohm or special.
  • signal generator make sinusoidal signal level about 2,8V max. In real life call tone is “beautiful dual tone or any ring bell” but simplify, it is 1 kHz sinusoidal.
  • Main powered means no battery, it is, power consumption is not first point.
  • any SMD speaker amplifier, quite general, not hifi… but, reason of “general” it means also speech must souds acceptable.

So, I ask, any recommendations of speaker amplifier and loudspeaker? My idea is quite simple: Some recommendations of the speaker amplifier circuit and loudspeaker. Then I have first step in this project and I can start design and testing…


I have found something for you to start out with , this is a simple amplifier and also a speaker .