creating a simple amplifier

Discussion in 'Power Electronics' started by Research Survey, Aug 20, 2016.

  1. Research Survey

    Thread Starter New Member

    Feb 27, 2016
    12
    0
    hello im a beginner here. can you guys please help me build a simple audio amp using the following

    bc 548b transistor
    4 ohm 0.5w speaker or d24mm Piezo Transducer
    i know i need to consult the datasheet to solve for the base collector emitter parameters but i dont know how.

    my source is a frequency generator using 555timer ic with potentiometer varying the frequency

    my desired output is something like this

    https://bryanduxbury.com/2012/01/20/one-transistor-audio-amplifier-for-arduino-projects/

    or this

    http://www.next.gr/circuits/buzzer-interfacing-with-pic16f877a-slicker-l48286.html

    i tried both circuits but it wont work.

    hoping someone can teach me how to make one and how to compute one

    many thanks in advance.
     
  2. AlbertHall

    Well-Known Member

    Jun 4, 2014
    1,931
    382
    You can connect the piezo direct to the '555 output, but note that they only work well at a particular frequency.
    You can also connect the speaker to the '555 output via a resistor - I would suggest 33 to 100 Ohms - that should make an audible noise (not very loud).
    If neither of these make any audible sound then the problem is with the '555 circuit and in this case please show us a schematic of how you are using the '555.

    Either of the circuits linked to will work - they are not going to produce stadium filling volume, but they should definitely be audible.
    If you are using the LM555 it can supply quite large currents so adding the single transistor won't add much so is probably not worth bothering with.
     
  3. Research Survey

    Thread Starter New Member

    Feb 27, 2016
    12
    0
    thank you sir for the fast response, the speaker or piezo produces sounds audible enough. but i hope to make it a little louder more by using simple components like transistor (active device) and a few resistor.
     
  4. AlbertHall

    Well-Known Member

    Jun 4, 2014
    1,931
    382
    Which '555 chip are you using (i.e. what letters come before the '555' on the chip)?
     
  5. Research Survey

    Thread Starter New Member

    Feb 27, 2016
    12
    0
    sir albert the top portion of the 555 ic was faded already .... but i remember the max current output is around 20- 25ma.
     
  6. absf

    Senior Member

    Dec 29, 2010
    1,492
    372
    Did you try the circuit below? You need 2 extra transistors BC337 & BC327. You can use bc548B as T1.

    Fig54aa.gif
    It is from the link here..... There are more audio amps at the bottom of the page with explanations.

    Allen
     
  7. ci139

    Member

    Jul 11, 2016
    341
    38
    it does not look like a failure unless you use PNP instead of NPN or messup the pinout using gain 1 collector to load instead emitter to load
    'huck - 10mA transistor ???? (5-.7)/104=.04 , 40mA×20=800mA starting current (the metal package can keep it a live for instant) use 3x2N2222 in parallel or higher power or mosfet or reduce your base current 160× e.g. use (5-.5)/5mA=900 - 4ohm speaker ×20 18kΩ
     
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