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    This audio limiter circuit is easy to build, works with BA741 8pins or 4pins so pay attention and uses a symmetrical power supply. When the audio input level is between 20mV and 20V the output will be a constant 25mV signal. Audio limiters can be used in a transmitter schematic or in any circuit you need a constant audio level.

    Audio limiter circuit schematic

    audio limiter compressor circuit schematic

    Audio limiter components
    R1 = 100K
    R2 = 1K
    R3 = 1M
    R4 = 68K
    R5 = 10K
    C1 = 10uF
    C2 = 680nF
    T1 = BFW11
    T2 = BC173C
    IC = BA741

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    15 Responses to "Audio Limiter Circuit"

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    1. we need this kind of circuit.is their any FET for replace BFW11,A equivalent.

    2. Paul Thompson says: on August 20, 2009 at 1:08 pm

      Is the chip BA741 the same as a LM741 cheers Paul

    3. I think, all J-fet op.amp. are equivalent:)
      Just the sound will be better…
      And you will have to change some resistors… (I don’t know yet, witch.)

    4. And I think, something is wrong… Because the ic 741 has just 8pins. On the schematic is 11pins:S

      • (Sorry: are 11pins:))

      • Hi,
        The + noninverting input should be to Pin 5 & NOT 8 as shown in the schematic! Pin 8 is NC- has no connection- in 14 pin PDIP 741 devices! So why not use an 8 pin 741 instead? This is more readily available than the 14 pin device & will take less space!

    5. Transistor T2 can not be NPN because have in the collector -15Vcc. Not polarized properly. And t2 the need of resistance in base.
      So, the circuit limited only one alternating audio signal; Not exactly pleasant!!!!!!!!!!!1

      • P. Marian ElectroSchematics.com says: on September 17, 2010 at 10:53 pm
          member

        You are so good! Yes, is not pleasant to hear that only one audio signal is alternating… I wonder why? And why the NPN transistor in NPN and not PNP… this is so strange, you genius! R5 is not in the base of T2?

      • Can you please send me your contact info ? I need someone with your knowledge to help design a new product. Thanks .. U.S. Miami, Florida 33141

      • The input has to be pulled up (polarized) at 5V for example so the music signal swings around 5V and not around 0V. This way both positive and negative sides of the input signal are attenuated.

    6. Realmente não funciona como deveria pois terá um má ou não funcionamento correto do transistor T2, sendo que R3 está polarizando o coletor de T2 como uma tensão negativa em relação ao terra que esta no emissor do mesmo, neste caso é como o terra fosse positivo na polarização do transistor…. deveria ser um PNP (ex.:BC559 OU EQUIVALENTE)

    7. can you help me. I want to output 3V when input is 2-10V.
      how to calculate circuit ?

    8. can you give corrected, working schematic?

    9. milesrhart says: on December 14, 2012 at 6:31 am
        member

      So what is a BA741? An OP amp?
      And does it have the same specs as an LM741?

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