LM1875 IC : PinOut, Datasheet & Its Working

Audio amplifier ICs are electronic devices that increase the audio signal strength by enhancing sound quality. So these ICs are used in various audio devices like portable speakers, stereo systems, home theaters, smartphones, etc. Audio amplifier ICs work in audio systems by using a small audio input signal to increase power to drive headphones or speakers to generate sound. Different letter symbols like Class A, B, C, Class D, and AB categorize these integrated circuits. So these ICs are available in typical semiconductor packages like; MSOP, HTSSOP, PDIP, TQFN & SOIC which can be through-hole or surface mounted. Thus, this article provides brief information on an audio amplifier IC like; the LM1875 IC, pinout, specifications, and applications.

What is LM1875 IC?

The LM1875 is a monolithic power amplifier IC, used in consumer audio applications. So the “LM” prefix within this IC stands for linear monolithic which means the analog components are incorporated into a single silicon piece. This power amplifier IC offers high-quality performance and very low distortion mainly for consumer-based audio applications. This IC delivers 20 watts on ±25V supplies into a 4 or 8-load.

This LM1875 IC utilizes very advanced circuit methods even at higher output power levels to attain less distortion levels. So it is compensated internally & stable for 10 or above gains. This IC has thermal shutdown and internal current limit to defend against overload.

LM1875 IC Working

The LM1875 monolithic power amplifier IC works based on different principles. This IC will shut down whenever the die temperature achieves 170 degrees Centigrade temperature, and it will restart whenever the temperature reduces to 145 degrees Centigrade. If the temperature increases again, then it will shut down at a temperature of 150°C. So it decreases stress on the integrated circuit and enhances its reliability.

This LM1875 IC utilizes superior circuit techniques even at higher output power levels to attain low distortion levels. So this IC has a wide range of supplies and operates with minimum external components. The internal current limit of this IC protects from an overload. This power amplifier IC has high gain, large o/p swing, fast slew rate, and high current ability.

LM1875 IC Pin Configuration:

The pin configuration of LM1875 IC is shown below. This IC includes five pins which are discussed below.

LM1875 IC Pin Configuration

Pin 1 (Non-Inverting Pin): This pin provides the input signal mainly to the amplifier.
Pin 2 (Inverting pin): This pin gives the feedback signal to the amplifier.
Pin 3 (-VEE): This is the negative power source of the amplifier.
Pin 4 (Output): This output pin is used to connect the amplifier to the speaker.
Pin 5 (V+): It is a positive power source pin that supplies power to the amplifier.

Features & Specifications:

The features and specifications of LM1875 IC include the following.

LM1875 IC is a high-performance-based audio power amplifier chip.
It is manufactured by Texas Instruments.
This amplifier IC has a fast slew rate, high gain, wide power bandwidth, large output voltage swing, high current capability, wide supply range, etc.
It needs the least external components for its operation.
It is available in the TO-220-11 single in-line package.
It has a low 0.015% THD (Total Harmonic Distortion) at 1 kHz, 20 watts.
This IC has internal thermal and short-circuit protection.
High Signal-to-Noise Ratio (SNR): 95 dB (typical)
Short Circuit Protection: Ensures robustness against load faults
Thermal Shutdown Protection: Protects against overheating
Low-frequency class AB amplifier most suited for audio amplification
Its operating voltage ranges from 16V to 60V.
It outputs up to 20 watts of power into a 4Ω or 8 Ω speaker at ±25V supply.
Its output current is 4 amps.
Open loop gain is 90dB.
Its bandwidth is 70 KHz.
Its input impedance typically is 150 kΩ.
Frequency response is from 10 Hz to 100 kHz.
Its slew rate typically is 4V/µs.
Its operating temperature range is from 0°C to +70°C.

Equivalent & Other Power Amplifier ICs

Equivalent LM1875 ICs are TDA2030 and TDA2050. Other audio amplifier ICs are; TDA1554, LM386, TDA7265, TDA7294, TDA2005 & TDA7279.

10W Audio Amplifier Volume Control Circuit with LM1875 IC

An audio power amplifier is an electronic amplifier used to amplify low-power audio signals to a high level that is sufficient to drive headphones or loudspeakers. So here we are designing a 10W audio amplifier circuit using LM1875 IC where the amplifier output volume can be controlled with a variable resistor.

Generally, LM1875 IC is a monolithic power amplifier that offers a low distortion range & large output voltage swing even at higher output power levels so that the speaker responds well to o/p audio signals.
Thus, this IC drives an 8Ω speaker, provides s10W output & delivers up to 30W whenever we utilize 30V bias. This IC includes thermal protection & internal o/p protection diodes which provide stable operation and are internally compensated for 10 or above gain.

The required components to make this circuit mainly include; resistors like; 4.7 KΩ, 2.7 Ω and 82 KΩ, 100 KΩ variable resistor or trimmer, capacitors like; 4.7 µF, 25V, 1000 µF, 35V, and 220 µF, 35V electrolytic capacitors, 0.22 µF ceramic capacitor, LM1875 audio amplifier IC, 8Ω, 10-W LS1 loudspeaker, a heat sink for IC, Two-point connectors for audio input & loudspeaker. Thus, connect this circuit as per the circuit shown below.

10W Audio Amplifier Volume Control Circuit with LM1875 IC

Working

The 10-watt audio amplifier circuit is shown below, designed with LM1875 amplifier IC and some passive components. This LM1875 delivers about 30W of output power based on the input voltage supply & output load impedance. So the power supply for this circuit is used according to the required output power which ranges from 5Volts to 15Volts DC.

Audio output from mobile or PC is provided to pin 1 of IC through VR1 variable resistor. The variable resistor in this circuit is used to control the amplifier output volume. The inverting pin is grounded through a capacitor and resistor. We know that op-amp is a negative feedback device, so a feedback resistor is connected between the inverting pin & output.

A series network is built with a resistor & capacitor for stability at the output pin. At last, an 8-OHM, 10-Watt loudspeaker is connected through a C3 capacitor which is used to filter out any available DC component.

Advantages & Disadvantages

The advantages of LM1875 ICs include the following.

The LM1875 power amplifier IC produces high-quality sound with less distortion.
It has excellent efficiency and comprehensive frequency response.
It amplifies high and bass frequencies well by creating a robust and well-rounded sound.
This IC is easy to implement, operate, and integrate due to its lack of additional parts and small footprint.
This IC has very low distortion levels.
It is designed mainly for high-quality based sound reproduction.
It has wide power bandwidth, high current capability, wide supply range, etc.
This IC operates with minimum components and dual or split power supply

The disadvantages of LM1875 ICs include the following.

If this IC is operated without a heat sink, the thermal protection circuit shuts down the amplifier.
The necessary heat sink dimension may be too large, particularly for some applications.
The output of this IC may be noisy when it is used as a high power and unity gain inverting operational amplifier.
When this IC is powered with a single supply, then its frequency response will be decreased particularly at the lower end.
Once it is powered with a single supply, then there will be an increased DC risk that enters into the speaker.
Whenever this IC is powered with a single supply, there may be an unexpected inrush of the current so it causes a “pop” on the connected speaker.
This IC should be used with a heat sink always because it generates a substantial quantity of heat during operation which causes harm to the device.

Applications

The applications of LM1875 ICs include the following.

LM1875 IC is for audio signal and high-power amplification.
This IC is used to cascade audio speakers.
It is used widely in audio applications.
This amplifier improves the sound experience in movie nights (or) music playing by generating high-quality audio amplification mainly for home theater installations.
This amplifier is suitable for public address systems utilized within conference rooms, auditoriums, and public areas because of its strong performance & capability to handle prominent speakers.
Musicians use this amplifier IC to amplify musical instruments like; keyboards or guitars by allowing them to play very louder during rehearsals, recording sessions, or concerts.
These ICs are used by audiophiles in DIY projects like designing bespoke stereo systems, headphone amplifiers, and bookshelf speakers.
These ICs may be used with vehicle audio installations to improve the car speakers’ audio output by delivering superior music quality as well as volume levels mainly for a more enjoyable driving experience.
This amplifier IC is used in broadcasting venues and professional recording studios for audio monitoring.
It may be used within audio-related labs to lecture sound amplification concepts, processing of audio signals, or even as a main part of student projects.

Please refer to this link for the LM1875 IC Datasheet.

Thus, this is an overview of LM1875 IC, pinout, features, specifications, circuit, working, advantages, disadvantages, and its applications. This audio power amplifier IC is used in various audio applications because of its benefits and features. So this is an attractive choice mainly for audio amplification because it is reliable and cheap. This IC is the best option for mainly audio amplification due to its wide range of applications, low cost, and high output level. Here is a question for you, what is an audio amplifier?