Hi all, I am using lm386n audio amplifier for increase voltage of (60mv ) with gain of 50 to the speaker .but out op -amp showing 1.2v instead of 1.5v volts. I am building amplifier circuit as same as given data sheet of lm386...
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Hi all, I am using lm386n audio amplifier for increase voltage of (60mv ) with gain of 50 to the speaker .but out op -amp showing 1.2v instead of 1.5v volts. I am building amplifier circuit as same as given data sheet of lm386...
Leo Bosch said:BTW: The external gain control is AC-coupled, the DC gain = 20, so when applying 60mVDC this will result in an output voltage of 1.2VDC.
Hi Leo, this is fully OT here but no way.. LM386 is not an operational amplifier but single supply operated audio/servo power amplifier, input can be symmetrical from ground offset compensated but output forever set to mid supply...
so DCOUT= 1/2VCC+(NI-INV)*DCGain. Ac coupled output cut away half VCC term so AC and DC gain are the same. Removing capacitor on feedback network also need adjustment of bias so some additional resistor are to be added to pin 7 to restore 1/2 VCC.
First place this forum is MSP430 related and this is OT.
sunil shetty said:your right 160mv *50 =3.0V ,instead of 3.V ,I written 1.5v ..( manual error ) . I am using pure sine wave of 500 HZ frequency . output not get saturated ..
This is impossible many way..
You have selected AC gain of 50, feeding 60mV RMS to input of this circuits to be in linear region need generate 3V RMS at output, this cannot be true if this circuit is powered by 5 volt rail!!
3V Rms need a swing of twice the rms value multiplied by squareroot of 2 so 3*2*1.4142 -> 8.485V this require add one more volt to compensate for junction drop and at least 9.5V power supply are required to have non saturated output, so @60mV in 5VDC supply, output is severely clipped (saturated).
Max reasonable output @5V are less than 3.5Vpp so max RMS output -> 1.23VRMS divided gain give max input RMS voltage -> 24.7 mV !!!
So to not saturate don't apply more than 20mV RMS or +13dBmV