Need help with audio amplifier

[pkpk614350]

Initially, I intend to divide the hold circuit into 3 parts which are the pre-amplifier, tone control and output stage. I found that the output stage need 7 volts to work but the power is just 4.5V battery. If using the op-amp to increase 4.5 volts to 9V is nearly impossible becoz the output of the op-amp is restricted by the power supply.. Would you guys give me some advice

 

[Nigel Goodwin]

4.5V is a really puny supply voltage, and you will get hardly any output power - increase the supply voltage.

What are you trying to do?.

 

[pkpk614350]

The project is only allowed to use 4.5volts battery for the portable audio amplifier.. At the moment, I really have no idea how to do it...

 

[Nigel Goodwin]

The project is only allowed to use 4.5volts battery for the portable audio amplifier.. At the moment, I really have no idea how to do it...

What are the full requirements?, 4.5V amplifiers are perfectly common, as are 3V ones - look at all the small portable radios. But like I said, power output is tiny.

 

[pkpk614350]

What are the full requirements?, 4.5V amplifiers are perfectly common, as are 3V ones - look at all the small portable radios. But like I said, power output is tiny.

The full requirement is nothing special. It's just using 3 AA battery (4.5volts) and must be produce an audiable sound comes out form the 8ohm small loudspeaker..

 

[CynicalMan]

The full requirement is nothing special. It's just using 3 AA battery (4.5volts) and must be produce an audiable sound comes out form the 8ohm small loudspeaker..

With these requirements, wouldn't it be overkill to include a preamp and a tone stage?

For the power amp or output stage, you might want to use an LM386.

LM386 Datasheet pdf - Low Voltage Audio Power Amplifier - National Semiconductor

They are cheap, common, can run on 4.5 volts, and work pretty well.

 

[audioguru]

Three AA battery cells are 4.5V only when they are new. The voltage drops to 3.6V quickly which is too low for an LM386 little power amplifier that has a minimum supply of 4.0V. With a 4.0V supply its output power at clipping into 8 ohms is only 0.061W which is almost nothing.

A TDA2822M is another little power amplifier (it is stereo) with a minimum supply voltage of 2V. Its two amps can be bridged then with a 4V supply its output at clipping into 8 ohms is 0.4W which is much more than the LM386. It also has only 8 pins.

With the TDA2822 bridged amp then tone controls can be used because there is enough power to add bass or treble boost without the amplifier clipping.