LM380 Audio Amplifier Working & Its Applications

The small-signal amplifier is a voltage amplifier that supplies their loads with enhanced amplifier signal voltage alternatively, power amplifier supply or large signal. The loads which operate with a large signal current to current are motors as well as speakers. In audio systems, the amplifier delivers high current compared with other operational amplifiers. This means the current used by the loads cannot be driven straight through the general-purpose amplifier’s output. This article discusses an overview of the IC LM380 audio amplifier and its applications.

What is an LM380 Audio Amplifier?

The LM380 IC is one kind of audio amplifier mainly used for power audio amplification. The internal design of this IC can be fixed by designers like 34dB. This IC includes a copper lead frame and features of this IC includes the range of supply is wide, less distortion; peak current is high, etc. Additionally, this IC offers high i/p impedance, voltage gain is fixed, less power drain, etc. This IC is the most frequently used device because of its high performance and cost-effectiveness.


Specifications of LM380

The specifications of this IC include the following.

  • Voltage supply range is from 10V to 222V
  • Standard DIP
  • Power drain is low like 0.13W
  • Distortion is less
  • Input impedance is high like 50kΩ
  • Fixed voltage gain at 50
  • Current supply capacity is 1.3A


We know that we always require a power supply to operate a device and the supply characteristics mainly depend on the device ratings. The ratings of this IC mainly include the following.

  • The voltage supply is 22V
  • Input voltage is 30V
  • Operating temperature is -0.3 to 6.3 V
  • Junction temperature is 1500C
  • Storage temperature is -65 to 1500C
  • Peak current is + or – 1A

Pin Configuration of LM380 Audio Amplifier

The pin configuration of this IC includes the following. This IC consists of 14-pins where each pin has its significance. These are pins are listed below. In this IC, some 6-pins have familiar functions namely GND pins. These pins play a significant role when we wish to attain exact results from that apparatus.

  • Pin 1: This is bypass pin
  • Pin 2: Non-inverting input
  • Pin 3: This is ground pin
  • Pin 4: This is ground pin
  • Pin 5: This is ground pi
  • Pin 6: inverting the input
  • Pin 7: This is ground pin
  • Pin 8: This is ground pin
  • Pin 9: NC
  • Pin 10: This is GND pin
  • Pin 11: This is ground pin
  • Pin12: This is ground pin
  • Pin13: NC
  • Pin14:+VCC

This pin-out diagram assists us to recognize the pin configurations of a device. So before going to use it, we have to look at the pinout diagram.

Alternate IC’s

The alternate ICs which belong to the same family mainly include the following.

The ICs are LM311, LM317, LM318, LM324, LM324N, LM335, LM339, LM348, LM358, LM380, LM386, and LM393

LM380 Audio Amplifier Circuit Diagram

The circuit diagram of the LM380 IC includes the following.


The circuit can be connected in four stages which include the following.

  • PNP emitter follower
  • Different amplifier
  • Common emitter
  • Emitter follower

1). PNP Emitter Follower

The input stage in the above circuit is emitter follower and it is composed of PNP transistors like Q1 and Q2. These transistors drive the differential pair of Q3 and Q4. The option of Q1 & Q2 input transistors permits the input to be positioned to GND i.e., the input is directly connected to any of the terminals of an amplifier like inverting and non-inverting terminals.

2). Differential Amplifier

The flow of current within the differential pair of Q3 and Q4 and this can be set up through resistor R3, transistor Q7, and voltage supply +V. The current mirror in the circuit can be formed using transistors like Q7, Q8, and connected resistors after that set up the collector current of transistor Q9.

Transistors Q5 and Q6 comprise of collector loads which can be used for the differential pair of transistors. The o/p of the differential amplifier can be taken at the Q4 and Q6 junction of transistors. This can be applied like an input to the voltage gain of the common emitter (CE).

3). Common Emitter

The amplifier stage of CE can be formed through ‘Q9’ transistor with diodes D1, D2 and Q8 transistor like a source load of current. The ‘C’ capacitor among the base and collector terminals of ‘Q9’ transistor, that offers internal recompense to help in establishing the higher cut-off frequency of 100 kHz. In the circuit, the current mirror can be formed using Q7 and Q8 transistors, the flow of current through diodes like D1 and D2 can be similar to the flow of current through resistor ‘R3’.

The diodes like D1 and D2 are temperature recompensing diodes used for Q10 and Q11 transistors. In that, the D1 and D2 diodes have similar characteristics as the BE (base-emitter) junctions of the Q11 transistor. Thus, the flow of current through transistors Q10, Q11& Q12 is approximately equivalent to the flow of current through D1 and D2 diodes.

4). Emitter Follower

Emitter follower can be formed through Q10 and Q11 NPN transistors. The blend of Q11 & Q12 transistors has the power capacity however the PNP transistor characteristics. The DC feedback which can be applied using ‘R5’ resistor is negative & it balances the differential amplifier so that the DC o/p voltage can become stable at +V/2;

The input stage in the circuit can be decoupled from the positive supply voltage through the pass capacitor in a sequence of a microfarad. So that must be coupled between the pin-1 and GND pin-7. The overall internal gain of the amplifier can be set at 50. But the gain can be improved through positive feedback.


The applications of the LM380 IC include the following.

  • TV sound systems,
  • Intercoms
  • Ultrasonic drivers
  • Line drivers
  • Alarms
  • Phonograph amplifiers
  • Some other applications of this mainly include AM radio, motor drivers, power converters, FM radio, servo, etc.

Thus, this is all about the IC LM380 audio amplifier datasheet used in consumer applications. In this amplifier, a gain of this can be fixed to 34 dB internally. Here is a question for you, what are the advantages of LM380 IC?

Image Sources: Texas Instruments

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