LM386 based audio amplifier

LM386 based audio amplifier: circuit Diagram 

The LM386 is an all – in – one Class AB amplifier IC which will be utilized in a spread of applications. LM386 IC has been in use for many years and remains getting used as Amplifier in Computer speakers and Portable Stereos. 

LM386 may be a low voltage power amplifier with an inactive power draw of 24mW, which makes it suitable for battery controlled applications. the foremost common package for LM386 is an 8 – pin DIP. the subsequent image shows the pinout diagram of the IC LM386

Circuit diagram of the LM386 based amplifier is shown in Fig. 2. it’s built around popular amplifier LM386 (IC1), an 8-ohm, one-watt speaker (LS1), four capacitors and a couple of other components. A 6V battery is employed to power this project.

LM386  audio amplifier
  • IC LM386
  • Condensor Mic
  • Speaker 8ohm
  • Capacitors- 220uF, 10uF (two), 0.1uF, 0.05uF
  • Resistor- 10k (two)
  • Potentiometer- 100k
  • Battery 5-12v

lm386 pinout

PIN 1 and 8:

These are the gain control PINs, internally the gain is about to twenty but it are often increased up to 200 by employing a capacitor between PIN 1 and eight .

we’ve used 10uF capacitor C1 to urge the very best gain i.e. 200. Gain are often adjusted to any value between 20 to 200 by using proper capacitor.

Pin 2 and 3:

These are the input PINs for sound signals. Pin 2 is that the negative input terminal, connected to the bottom . Pin 3 is that the positive input terminal, during which sound signal is fed to be amplified.

In our circuit it’s connected to the positive terminal of the condenser mic with a 100k potentiometer RV1. Potentiometer acts as volume control knob.

A capacitor C5 of 0.1uF has also been used along side potentiometer, to get rid of the DC component of input and only allow audio (AC component) to be fed into LM386.

Pin 4 and 6:

These are the facility supply Pins of IC, Pin 6 for is +Vcc and Pin 4 is Ground. The circuit are often powered with voltage between 5-12v.

Pin 5:

this is often the output PIN, from which we get the amplified sound signal.

The output has both AC and DC component, and DC component is undesirable and can’t be fed to Speaker. So to get rid of this DC component, a capacitor C2 of 220uF has been used. This has an equivalent function as Capacitor C5 (0.1uF) at input side.

Along with this capacitor, a filter circuit of Capacitor C3 (.05uF) and resistor R1 (10k) has been used at the output PIN 5. This filter also called the “Zobel network”, this filter is employed to get rid of the sudden High frequency oscillations or noise.

Pin 7:

this is often the bypass terminal. It are often left open or are often grounded employing a capacitor for stability.

Design of LM386 amplifier Circuit

The design of LM386 amplifier Circuit is extremely simple. First, connect the facility supply pins (Pins 6 and 4) to 12V and Ground respectively. Note that the utmost power supply for LM386 is 15V.

Next, we’d like to attach the input. The input are often given from any audio source like mobile or a microphone. we’ve given the audio input from a mobile using the three .5mm connector.

NOTE: Simple 3.5mm connector (without microphone) will have three connections: Left Audio, Right Audio and Ground. Since LM386 may be a Mono amplifier , we’d like to attach either the Left audio or the proper Audio from the source along side ground.

Alternatively, both the channels are often combined to supply a mono channel using appropriate resistors.

Audio Jack

If we would like to regulate the extent of the input, we’d like to attach a ten KΩ Potentiometer at the input. Since we do this on a breadboard, we didn’t connect any input volume control POT. Additionally, alittle capacitor are often connected serial with the input to filter the DC Components.

Internally, the gain of the LM386 amplifier is about to twenty (without any gain control circuitry). We connected a ten µF Capacitor between the gain control pins i.e. pins 1 and eight . Hence, the gain is now set to an element of 200.

Although the info sheet of LM386 says the bypass condenser at Pin 7 is optional, we found that connecting a 100 µF capacitor was really helpful because it helps in reducing the noise. It are often left open for normal operation.

Finally, for the output, first connect a 0.05 µF Capacitor and a ten Ω Resistor serial between the output pin (Pin 5) and ground. This forms a Zobel Network, a filter consisting of resistor and capacitor serial and is employed to repair the input impedance of the driving force .

Next is that the speaker connection. LM386 can drive any speaker within the impedance range of 4 Ω to 32 Ω. we’ve used a 4 Ω Speaker. Connecting the speaker through an enormous 1000 µF capacitor was really helpful because it filtered out the unnecessary DC signals.

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