How to Control Gain for the IC LM386
In order to make the IC better with its response, its pin#1 and 8 have been attributed with a gain control facility which may be set externally.
Gain simply means the capacity or the amplifying level of the device up to which it is able to amplify the applied input low signal audio input.
When the above pin outs are kept unconnected to anything, the internal 1.35K resistor sets the gain of the IC to 20.
If a capacitor is joined across the above pin outs, the gain is suddenly lifted to 200.
The gain may be simply made adjustable by connecting a pot in series with the above explained capacitor across the pin 1 and 8.
Practical Application Amplifier Circuits Using the IC LM386
The following figure shows a typical IC LM386 amplifier circuit having the bare minimum number of components required to make the IC operate at its internally set level of gain 20.
Having Gain of 20
The speaker used is a 2 watt, 8 Ohms type.
The input at Vin may be fed from any audio source such as a cell phone headphone socket, a CD/DVD player RCA L or R socket or any other similar source.
The pin Vs should be connected to +12V DC supply from an AC DC adapter or a home made transformer/bridge power supply unit.
Pin #4 should be connected to ground or the negative of the power supply.
The earth wire or the negative wire from the input audio source should also be connected to the above negative of the power supply.
The input pin#2 goes to a 10K pot which becomes the volume control, one of its end terminals is picked for receiving the input signal while the other end is connected to ground, the center one goes to the hot end of the IC.
The speaker is connected to in #8 via a high value blocking capacitor, the resistor/capacitor arrangement connected across pin #5 and ground has been included for frequency compensation and to provide greater stability to the circuit.
Having Gain of 200
The next circuit shows a similar design as above, except that its pins 1 and 8 have been connected to a capacitor of 10uF, which as explained above helps to pull the gain of the amplifier to 200
Application Circuits
From the above discussion we have learned that the LM386 is versatile little audio amplifier IC which can be applied in many different small audio related circuits quickly and with great efficiency.
The following are a few application circuits using IC LM386 which you an build and have a lot of fun.
The last component of the circuit is a typical LM386 amplifier with an 8-ohm output and a gain of 200. The output of the IC LM386 may be connected to any compatible speaker or earphone.
Due to the coupling between S1 and R4, the AF/RF Signal tracer may be turned on and off by adjusting the volume, just like a battery-operated radio. A total of four AA batteries in a suitable holder serves as the power supply.
Simple Buzzer Circuit
An exact buzzer-like sound is produced by the circuit displayed below. Just a couple of ICs and a few other parts are needed to build this circuit.
Through resistors R1 and R2, C1 begins to charge as soon as S1 is briefly pushed. In the end, it activates pin 2 of IC1's 555 oscillator/timer.
The IC subsequently starts discharging the capacitor by pushing pin 7 low via R2. As long as S1 remains pushed ON, this cycle happens repeatedly.
The pin#3 output of IC1 switches ON/OFF in response to the capacitor's charging and discharging, providing a sound frequency to IC2. IC2 is an LM386 low-voltage audio power amplifier that boosts the loudness of the tone frequency.
The sound frequency from IC1, which sounds like a genuine buzzer, is amplified by IC2 and reproduced through the speaker.
For a low-frequency buzzing sound, you can increase the value of C1 to 0.1 uF. For improved stability, you may also use a 47-F capacitor to bypass pin 7 of IC2 to ground.
How to Control Gain for the IC LM386
In order to make the IC better with its response, its pin#1 and 8 have been attributed with a gain control facility which may be set externally.
Gain simply means the capacity or the amplifying level of the device up to which it is able to amplify the applied input low signal audio input.
When the above pin outs are kept unconnected to anything, the internal 1.35K resistor sets the gain of the IC to 20.
If a capacitor is joined across the above pin outs, the gain is suddenly lifted to 200.
The gain may be simply made adjustable by connecting a pot in series with the above explained capacitor across the pin 1 and 8.
Practical Application Amplifier Circuits Using the IC LM386
The following figure shows a typical IC LM386 amplifier circuit having the bare minimum number of components required to make the IC operate at its internally set level of gain 20.
Having Gain of 20
The speaker used is a 2 watt, 8 Ohms type.
The input at Vin may be fed from any audio source such as a cell phone headphone socket, a CD/DVD player RCA L or R socket or any other similar source.
The pin Vs should be connected to +12V DC supply from an AC DC adapter or a home made transformer/bridge power supply unit.
Pin #4 should be connected to ground or the negative of the power supply.
The earth wire or the negative wire from the input audio source should also be connected to the above negative of the power supply.
The input pin#2 goes to a 10K pot which becomes the volume control, one of its end terminals is picked for receiving the input signal while the other end is connected to ground, the center one goes to the hot end of the IC.
The speaker is connected to in #8 via a high value blocking capacitor, the resistor/capacitor arrangement connected across pin #5 and ground has been included for frequency compensation and to provide greater stability to the circuit.
Having Gain of 200
The next circuit shows a similar design as above, except that its pins 1 and 8 have been connected to a capacitor of 10uF, which as explained above helps to pull the gain of the amplifier to 200
Application Circuits
From the above discussion we have learned that the LM386 is versatile little audio amplifier IC which can be applied in many different small audio related circuits quickly and with great efficiency.
The following are a few application circuits using IC LM386 which you an build and have a lot of fun.
The last component of the circuit is a typical LM386 amplifier with an 8-ohm output and a gain of 200. The output of the IC LM386 may be connected to any compatible speaker or earphone.
Due to the coupling between S1 and R4, the AF/RF Signal tracer may be turned on and off by adjusting the volume, just like a battery-operated radio. A total of four AA batteries in a suitable holder serves as the power supply.
Simple Buzzer Circuit
An exact buzzer-like sound is produced by the circuit displayed below. Just a couple of ICs and a few other parts are needed to build this circuit.
Through resistors R1 and R2, C1 begins to charge as soon as S1 is briefly pushed. In the end, it activates pin 2 of IC1's 555 oscillator/timer.
The IC subsequently starts discharging the capacitor by pushing pin 7 low via R2. As long as S1 remains pushed ON, this cycle happens repeatedly.
The pin#3 output of IC1 switches ON/OFF in response to the capacitor's charging and discharging, providing a sound frequency to IC2. IC2 is an LM386 low-voltage audio power amplifier that boosts the loudness of the tone frequency.
The sound frequency from IC1, which sounds like a genuine buzzer, is amplified by IC2 and reproduced through the speaker.
For a low-frequency buzzing sound, you can increase the value of C1 to 0.1 uF. For improved stability, you may also use a 47-F capacitor to bypass pin 7 of IC2 to ground.
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