For Single transistor Amplifier for Mobile.

Discussion in 'General Electronics Chat' started by anil007, Jul 24, 2012.

  1. anil007

    Thread Starter New Member

    Jul 24, 2012
    Hi Folks,

    Good Day to all. This is Anil from Chennai, India.

    Let me discuss the required topic.
    I am having a G5 mobile (model W570) which is a discontinued model. The problem is it has only very low earpiece volume(even when the setting are high / maximum). I tried to service many times but no use, Even the authorized service centre cant help. When I use the headphone the sound is Ok, also when using in Speaker phone mode the output is Ok. Only problem is the built-in earpiece speaker (30Ω) has low volume output, even when the setting is MAX.

    I opened the mobile and has the following details. The earpiece speaker impedance is 30 ohm. (This speaker can be taken out - connected by Wire)
    The input impedance to the earpiece speaker is 2.1 KΩ. That is they have bypassed a resistor of 2.1 KΩ on the PCB.

    I tried to get lower impedance ear piece speaker like ( 20 Ω / 15 Ω) but it it is not available in market.

    My question is can we use a single transistor amplifier with Tr. BC548 or any other miniature type NPN transistor to increase the volume.

    Even though I am a Diploma holder in Electronics, I am not having that much design ideas to create a transistor amplifier.

    On the board I have 2 terminals marked + & - for ear piece speaker connection. I hope the (-) terminal will be common and we can design a common emitter single Transistor amp. From the + terminal I think we can feed the base voltage / input to the transistor Amp.

    The power supply may be ranging from 3 to 5V. The IMP thing to be kept in mind is the count of components must be kept very low, because it must fit in the mobile cover. (only 1 transistor + 2/3 other associated components)

    Hope you guys have got a clear picture of my proposed design aspect.

    Please post your valuable feedback with Ckt diagram or design ideas.

    Have a great day.

    Mob : <SNIP>
    email: <SNIP>
    Last edited by a moderator: Jul 24, 2012