Amplifier Circuit DiagramsPower SuppliesVoltage Regulators Circuit Diagrams

Voltage Regulator as Audio Amplifier Schematic Circuit Diagram

The LM338 voltage regulator can also be used as an audio amplifier. The output voltage can be controlled by varying the IC’s reference voltage (pin 1), which is reflected as the output signal in the speaker. The IC can handle up to 5amp current.

Circuit and working

The audio amplifier’s circuit diagram is depicted in Figure 1. It comprises components such as an LM338 voltage regulator (IC1), BC548 transistor (T1), several resistors (R1 through R7), two potentiometers (VR1 and VR2), a loudspeaker (LS1), and a variety of other elements.

Voltage Regulator as Audio Amplifier Schematic Circuit Diagram 1

Fig. 1

LM338 is arranged in a class-A amplifier configuration. Initially, it establishes its output voltage at the midpoint of the maximum output voltage range. When it receives an audio signal, the output signal oscillates on both sides of this midpoint voltage. This audio signal is then directed to the speaker through a capacitor (C3), which serves to block any DC components while allowing only the audio signal to reach the speaker.

Transistor T1 takes charge of regulating the reference voltage of the IC in accordance with the input signal it receives at its base.

The circuit operates on a 12V DC power source with a current rating of 1A, which can be conveniently supplied by a battery or another suitable power supply.

Voltage Regulator as Audio Amplifier Schematic Circuit Diagram 2

Construction and testing

An actual-size PCB layout for the voltage regulator as the audio amplifier is shown in Fig. 2 and the layout of its components in Fig. 3.

Construction and testing

Fig. 2

Voltage Regulator as Audio Amplifier Schematic Circuit Diagram 4

Fig. 3

After assembling the components on the PCB, disconnect jumper SJ1, set VR1 to a minimum, and turn switch S1 ‘on.’ Verify voltages as shown in the table.

Voltage Regulator as Audio Amplifier Schematic Circuit Diagram 5

Configure VR2 to achieve approximately 10V DC at TP2, then proceed to reconnect jumper SJ1. You can now connect any audio signal as an input to CON1. To adjust the output volume, VR1 can be utilized. Finally, encase the circuit within a suitable enclosure, and it will be ready for use.

The LM338 is a versatile 3-terminal positive voltage regulator with adjustable capabilities, capable of providing over 5A of current across an output range spanning from 1.2V to 32V. This article will introduce the LM338, covering its pinout, features, application circuits, datasheet, and additional pertinent information.

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