AM Radio Power Amplifier Circuit Diagram

Introduction

Radio is a crucial form of communication that has been a popular medium for more than a century. It is used for entertainment, education, and emergency communication. However, the signals received by the radio waves are very weak and need amplification before they can be converted into audio signals. This is where power amplifiers come into play. An AM Radio Power Amplifier using LM390 IC is an excellent solution for amplifying the audio signal of AM radios efficiently.

What is LM390 IC?

The LM390 is a monolithic power amplifier designed for high-performance audio and a wide range of applications. This IC is rated for operation over the industrial temperature range of -40°C to +85°C. It has a high voltage gain of 100, and it can handle a maximum output current of 1A. The LM390 is an excellent choice for amplifier designs requiring high output power and low distortion.

Circuit Diagram

of AM Radio Power Amplifier

Following is the circuit diagram of this project, which will guide you to build the project easily and smoothly.

**AM Radio Power Amplifier Circuit Diagram**

NOTE:-

1: Twist supply lead and supply ground very tightly.
2: Twist the speaker lead and ground very tightly.
3: Ferrite bead is Ferroxcube K5-001-001/38 with 3 turns of wire.
4: R1C1 band limits input signals. Note 5: All components must be spaced very close to IC.

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Why choose the LM390 IC for AM Radio?

The LM390 IC is an excellent choice for the AM radio power amplifier due to its versatility, simplicity, and low cost. The LM390 IC improves the audio quality of the AM radio system significantly. It provides a high gain and low input impedance that enable it to accept weak AM radio signals and convert them into high-quality audio signals. Additionally, the LM390 IC’s output stage can deliver up to 1A of current, providing sufficient power to drive the speaker.

Design of Power Amplifier for AM Radio using LM390 IC

The Power Amplifier design for AM Radio using the LM390 IC comprises the following components:

Input Coupling Capacitor
The input coupling capacitor (C1) is a polarized capacitor that blocks the DC signal, allowing only the AC signal to pass through. Its value determines the impedance of the input circuit, and a value of 4.7µF is appropriate.

Input Resistor
The input resistor (R1) is used to bias the input signal and improve the amplifier’s stability. It also determines the input impedance of the amplifier. A value of 1KΩ is suitable for this design.

Volume Control Potentiometer
The volume control potentiometer (RV1) is used to vary the output level of the amplifier. A 10KΩ potentiometer can be used for this purpose.

LM390 IC
The LM390 IC is the heart of the design, and it provides the necessary amplification of the input signal. It is essential to connect the IC properly to avoid any damage to the IC.

Output Capacitor
The output capacitor (C2) is a non-polarized electrolytic capacitor that blocks the DC component of the output signal, allowing only the AC component to pass through. A value of 220µF is suitable for this design.

Speaker
The speaker is the final stage of the amplifier and converts the amplified signal into sound.

Power Supply
The power supply is an essential component of the design, and it is required to provide the necessary voltage and current to the LM390 IC. A 12VDC power supply is suitable for this design.

Working Explanation

of AM Radio Power Amplifier

Working Principle of Power Amplifier for AM Radio using LM390 IC

The power amplifier for AM Radio using LM390 IC amplifies the weak input signal received from the AM radio and converts it into high-quality audio. The input signal is applied to the input coupling capacitor (C1), which blocks the DC component, allowing only the AC component to pass through. The input resistor (R1) biases the input signal, and the volume control potentiometer (RV1) allows the user to vary the output level.

The amplified signal is then passed through the output capacitor (C2), which blocks the DC component, allowing only the AC component to pass through. The amplified signal is then applied to the speaker, which converts the amplified signal into audible sound.

The LM390 IC amplifies the signal by providing the necessary voltage gain and current gain. The voltage gain is set by the resistor (R3) and the capacitor (C3), while the current gain is determined by the output stage of the LM390 IC. The LM390 IC has high input impedance and low output impedance, making it efficient for driving the speaker.

Conclusion

The AM Radio Power Amplifier using LM390 IC is an excellent solution for amplifying the audio signal of AM radios. The LM390 IC provides a high gain and low impedance that makes it suitable for amplifying weak AM radio signals. Additionally, the LM390 IC’s output stage can deliver up to 1A of current, providing sufficient power to drive the speaker. The simplicity and low cost of this design make it a popular choice for DIY enthusiasts and hobbyists.