Simple 15W Class B Audio Amplifier Circuit

An audio amplifier is an important part of sound systems because it boosts weak audio signals into strong ones that can power speakers.

This specific simple 15W Class B audio amplifier is designed to deliver clear and powerful sound, making it a great option for home audio systems or DIY projects.

It uses the IC LM833 operational amplifier at the beginning of the process, which works well with special NPN and PNP transistors to provide effective amplification.

This smart design helps reduce distortion and improve efficiency making it perfect for many different audio uses.

Circuit Working:

Parts List:

In the above circuit diagram the audio input signal goes through a special AC coupling system using a capacitor called C3.

This capacitor sends the signal to the non inverting input which is pin 3 of the LM833 operational amplifier known as IC.

Its main job is to block any direct current DC parts of the input signal letting only the alternating current AC audio signal pass through.

There is also a resistor R3 with a resistance of 1M that helps set a reference point to ground for the incoming signal.

The first part of the LM833 represented by IC amplifies this input signal and how much it amplifies depends on some external feedback components that are set up inside the circuit.

You can find the amplified output at pin 7, which then goes to the base of an NPN transistor called Q1 specifically a TIP41 model.

The transistors Q1 TIP41 NPN and Q2 TIP42 PNP are arranged in a complementary push pull setup.

This setup is really good at amplifying the signal while also reducing crossover distortion which is a common problem with Class B amplifiers.

To help with the biasing of the transistors a diode named D1 which is a 1N4148 is used to make the transitions between the on and off states of Q1 and Q2 smoother.

Additionally, capacitor C1 is important for keeping things stable and filtering out any unwanted frequencies from the amplified output.

Capacitor C2 acts as a coupling capacitor that blocks any DC components from getting to the load which in this case is the speaker.

The whole circuit runs on a symmetrical dual power supply that provides +12V and -12V DC, which is necessary to give enough headroom for amplifying the signal.

The boosted signal powers an 8 ohm speaker, which can handle up to 15 watts of maximum power.

Formulas with Calculations:

Following formulas can guide your for designing a Simple 15W Class B Audio Amplifier Circuit:

Power Output (P):

P = (V_peak^2) / (2 * R)

where,

• V_peak is the peak voltage of the output signal.
• R is the speaker impedance for 8 ohms.

For a peak voltage of approximately 15.5V:

P = (15.5^2) / (2 * 8)
P = 240.25 / 16
P = 15W

Voltage Gain (A):

A = V_out / V_in

where,

• V_out is the amplified output voltage.
• V_in is the input signal voltage.

How to Build:

To build a Simple 15W Class B Audio Amplifier Circuit follow the below mentioned connections steps:

• Assemble all the components as mentioned in the above circuit diagram.
• Connect pin 1 of IC1 LM833 to pin 2, via to third leg of VR1 pot.
• Connect pin 3 of IC1 LM833 to audio input through capacitor C3, connect from pin 3 to GND resistor R3.
• Connect pin 4 of IC1 LM833 to -12V supply voltage.
• Connect pin 5 of IC1 LM833 to GND.
• Connect pin 6 of IC1 LM833 to center leg of VR1 pot.
• Connect pin 7 of IC1 LM833 to one end of 8Ω speaker as shown in circuit diagram through capacitor C1.
• Connect pin 8 of IC1 LM833 to +12V positive supply volatge.
• Connect the first leg of VR1 pot pin 7 of one end of 8Ω speaker and other end of speaker to GND
• Connect capacitor C2 from pin 7 to base of transistor Q2.
• Connect base of transistor Q1 to -12V through diode D1 and resistor R1 in series, connect collector of Q1 to +12V supply and connect emitter of Q1 to emitter of Q2.
• Connect base of Q2 to pin 7 of IC1 LM833 through capacitor C2, connect collector of transistor Q2 to -12V, and connect emitter of transistor Q2 to emitter of Q1

Conclusion:

The simple 15W class B audio amplifier circuit is an easy to build and effective option for low power audio projects.

It uses the IC LM833 chip along with matching transistors to create a good mix of sound quality and energy use.

When built and tested correctly it produces very little distortion and delivers clear sound which makes it a great pick for both hobbyists and audio fans.

References:

Datasheet IC LM833