[SOLVED] problem in apmplying the analouge signal using LM386

[abhishekdixit]

Hello,
I have to apmplify 1V analouge audio signa. I hav used 4ohm 25watt speaker at the output. And according to datasheet I hav designed my circuit with the gain 200db. When I see my output on the oscilloscope, my amplifier is not capable to amplify it 200times. Due to this the output is not clear.I have given it 12V as a supply voltage. Pease help me what should I do now?

With regards,
Abhishek Dixit

 

[ashugtiwari]

without circuit, its difficult to answer, but just a tip for u:
the amp o/p for LM386 will be too low to drive such low impedance speaker, in long aho i tested it to be something around 550mW.
To make it simple, all headphones/speakers require a certain amount of power to be driven at a certain acoustic level, this is the sensitivity of the headphones/speakers, it's expressed in dB/mW (decibel per milliwatts).
Considering P = U^2 / R = R * I^2 (Power = Voltage squared divided by impedance = Impedance times Intensity squared) and headphones/speakers with the same sensitivity:
- with low impedance headphones/speakers you need more current to achieve the desired acoustic level.
- with high impedance headphones/speakers, you need more voltage to achieve the desired acoustic level.

In addition to that, there's always the damping factor to consider (headphone impedance / amplifier impedance), it's usually recommended to have a damping factor greater than 10, ie. with 300 ohms headphones, use an amp with a maximum output impedance of 30 ohms.
In short, with high impedance headphones, you need an amp with more voltage swing and with low impedance headphones an amp with more current capacity and a lower output impedance.

i suggest, use push pull configuration for high current o/p and instrumentation amp configuration for high voltage o/p.

hope that helps.

 

[abhishekdixit]

Hello,
Thanks for your help, but can you Please tell me that what was the value of your input voltage at the time of testing??