Very urgent:op map amplification

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T

tuck

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Sorry to interrupt u all.

But i really cannot done it by myself.

I'm a univesity student and this this 1 of my assignment to summit by next week.

I'm using a op amp to amplify an AC 5V to around 7-8V to drive a 8 ohm speaker.

but i juz cann't get it right.

I been recommanded to use a IC chips call LM 386 to do the amplification.

but the software i use didn't have this IC chips data, and i don't know how to connect it.

if anybody know how to solve it, pls reply me n pls show me how to do it.

Thanks.
 
Last edited:
You don't need an opamp, it can't drive a speaker - you need a power amplifier, of which an LM386 is a small common example.
 

If you have to use opamp, you need to add a power output stage made from power transistors. Or use a pre-made power amplifier as suggested.
Opamp devices by themselves cannot deliver 7-8V into an 8 Ohm load.
 
Thanks for reply

My idea is to set a gain to amplify 5V to 7-8V.

so the op amp will act as a power amplifier.

The design software i use called Pspice didn't have LM386 this IC chips.

N i try to use a normal multistage op amp to set the gain as 100.

so the output voltage will suppose to reach around 7-8V which i wanted.

but i cannot get it n somehow i got a negative voltage!!
 
Last edited:
The LM386 is for low power, like in a clock radio.
With a 6V supply, it clips with only 200mw into an 8 ohm speaker.
With a 9V supply it clips with only 450mW into an 8 ohm speaker.
With a 12V supply it gets very hot at clipping which is only 530mW into an 8 ohm speaker.

An opamp clips with an output power of only 1.5mW into an 8 ohm speaker. You would barely hear it if the speaker is against your ear.
 

Again, even if your circuit is connected correctly with a gain of 100, IT WILL NOT BE ABLE TO DRIVE 8 OHMS. It will go into current limit and you will not get your 7-8V on the output.

The opamp will act as a power amplifier ONLY if it can handle the load.

Your negative voltage, is it near the negative power supply? You probably have a wiring error or a simple mistake. It would be helpful for you to post your schematic.
 
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