For Single transistor Amplifier for Mobile.

Thread Starter


Joined 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>
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