Amplifiers in any high-performance audio system improve the audio source’s signal strength by ensuring optimal fidelity &power delivery to loads. Similarly, the power amplifier is one of the main amplifiers used in high-performance audio systems. So these amplifiers amplify signals and control the performance of a speaker with stability and compatibility in different audio systems. So power amplifiers, are significant in high-performance-based audio systems to ensure fidelity & sound clarity. They often have some features like current limiting, thermal protection, and impedance matching to protect both the amplifier and loads connected from damage. So its selection and incorporation of particular applications is significant to improve audio playback systems and improve the listening experience. This article elaborates on the LM3876 IC, pinout, features, specifications, and applications.
What is LM3876 IC?
The LM3876 IC is a high-performance-based audio power amplifier, available in the 11-Lead TO-220 Package. So this IC delivers continuous 56 watts of average power to an 8ohms load with 0.1% THD+N from 20Hz to 20 kHz frequency. This IC maintains an outstanding > 95dB S/N ratio with a 2.0µV typical low noise floor. It exhibits 0.06% very low THD+N values at the rated o/p into the rated load above the audio spectrum. So it provides first-rate linearity with a 0.004% typical IMD rating.
The LM3876 IC uses its SPiK (Self Peak Instantaneous Temperature) protection circuitry by placing it in a class above hybrid & discrete amplifiers by providing a dynamically and inherently protected SOA (Safe Operating Area). The SPiKe protection ensures that these components receive complete protection at the output from under-voltage, overvoltage, overloads like shorts to the supplies, thermal runaway, and instantaneous temperature peaks.
How LM3876 IC Work?
The LM3876 IC works as a high-performance-based audio power amplifier that changes DC to an AC voltage signal from the power supply. This IC uses SPiKe protection circuitry that protects from thermal runaway, overloads, under-voltage, overvoltage, etc. So this amplifier IC maintains a high signal-to-noise ratio, excellent linearity, low THD+N, and low noise floor. The LM3876 audio power amplifier delivers 56 watts of continuous average power.
LM3876 IC Pin Configuration:
The pin configuration of LM3876 IC is shown below. So this IC includes 11 pins which are explained below.
LM3876 IC Pin Configuration
- Pin-1 (V+): Positive Supply Voltage
- Pins 2, 5, 6 & 11 (NC): These are no connection pins of the audio amplifier IC.
- Pin-3 (Output): This is an output pin of an audio amplifier IC.
- Pin-4 (V-): It is a negative (-Ve) voltage supply pin of the IC.
- Pin-7 (GND): It is a ground pin of the IC.
- Pin-8 (MUTE): It is a mute pin of the amplifier IC.
- Pin-9 (Vin-): It is a negative input voltage pin of the IC.
- Pin-10 (Vin+): It is a positive input voltage pin of the IC.
Features & Specifications:
The features and specifications of LM3876 IC include the following.
- LM3876 IC is a high-performance audio power amplifier.
- This IC is available in an 11-Lead TO-220 package.
- It provides 56 watts continuous average o/p power in 8Ω load.
- It is capable of 100 watts of instantaneous peak output power.
- Minimum signal-to-noise ratio is ≥ 95 dB.
- It has an input mute function.
- The internal current limiting circuitry protects its output from a short to GND (or) to the supplies.
- This IC has a SPiKe (Self Peak Instantaneous Temperature) protection circuit that safeguards the amplifier from thermal runaway, overloads, etc.
- This IC has a 2.0µV low noise floor & a S/N > 95dB.
- This IC works with 18V minimum & 84V maximum voltage.
- It has 0.1% of THD+N at 20Hz to 20 kHz frequency.
- This IC has a 0.004% IMD typical rating.
- Its operating temperature ranges from −20°C ≤ TA ≤ +85°C.
- The max junction temperature is 150°C and SOA temperature is almost 250°C.
Equivalents & Alternatives
Equivalent to LM3876 IC is LM3886 IC. Alternative audio amplifier ICs are; TDA2005, LM386, LM380, LM2002, LM383, D2030A, LM1875, TDA7293, TDA1521, TDA7294, etc.
50 Watts Audio Amplifier Circuit with LM3876 IC
Audio amplifiers are significant within sound systems because they amplify weak audio signals and generate sound through loudspeakers. The required components to make this audio amplifier circuit mainly include; resistors like 20k, 2.7Ω, 1k & 22k, capacitors like 100nF, 22μF, 3.3μF, 220μF & 100μF, LM3876 IC, ON / OFF mute switch, 0.7μH Inductor, and 8Ω 50 watt speaker.
The connections of this 50 Watts audio amplifier circuit with LM3876 IC follow as follows;
- Connect pin-1 of IC to +35V positive supply.
- C1 & C2 capacitors connected to GND from a positive supply.
- Connect pin-3 to one end of the load through the R7 resistor and the other end to GND.
- Connect the R6 resistor and C8 capacitor in series & GND between the R2 and R7 resistors.
- The L1 inductor must be connected as shown in the following circuit.
- Connect pin-4 to -35V negative supply.
- Connect pin-7 to GND of LM3876 IC.
- The pin-8 of the IC must be connected to the C6 capacitor & GND. Connect R3 & S1 in series from pin-8 to -35V supply.
- Connect R4 resistor & C3 capacitor from -35V & GND.
- Connect pin-9 of LM3876 IC to GND using R1 resistor and C5 capacitor in series.
- Resistor R2 must be connected from pins 3 & 9 of IC
- Connect pin-10 of LM3876 IC to audio IN using R4 & C7 in series.
- Connect R5 resistor between C7, R4 & GND.
50 Watts Audio Amplifier Circuit with LM3876 IC
Working
The LM3876 IC works with a dual voltage supply that ranges from +/-12V to +/-49V DC but this circuit uses +35V supply voltage. When the audio signal enters the pin 10 through C7 then it blocks the DC voltage of the input signal. Here, the R5 resistor biases and checks whether the impedance is properly matched or not.
The amplifier gain is decided by R1 & R2 resistors. Capacitors C1 & C3 from the power supply reduce higher frequency noise. Capacitors C2 & C4 stabilize the power supply through filtering out less frequency ripples. Here, the R3 resistor helps in controlling the mute function by allowing a 0.5mA current supply from pin-8 of the IC to turn the mute off with the S1 switch.
The L1 inductor and R7 resistor create a Zobel network, that keeps the below circuit stable and decreases high-frequency oscillations. Here, the C8 capacitor helps in filtering the output. You can transmit the amplified audio signal to an 8Ω loudspeaker that connects to pin-3. So this circuit powers the speaker effectively with a 50-watt clear output. The LM3876 IC includes in-built protection from short circuits & overheating which makes it consistent in different situations.
Turns Calculation:
The number of required turns can be calculated by using an air core inductor formula.
L = (N² * μ₀ * A) / l
‘L’ is the inductance within henries.
‘N’ is the number of turns.
‘μ₀’ is free space permeability.
‘A’ is the cross-sectional region of the coil.
‘l’ is the coil’s length.
Voltage Gain:
You can calculate the voltage gain of this amplifier using the following formula.
G = 1 + (R2 / R1)
Substitute the resistor values:
R1 = 1,000Ω and R2 = 20,000Ω
Substitute these values in the above equation, so we can get the following value.
G = 1 + (20,000 / 1,000) = 21
Power Output:
You can measure this amplifier’s RMS power output with the formula below:
P = (Vrms²) / R
If we assume Vrms = 20V and R = 8Ω then we can get the below value.
P = (20²) / 8 = 50 watts.
Thus, 50 watt audio amplifier circuit uses the LM3876 IC which is an effective and dependable choice used for great sound quality. This IC has some in-built security features that make it ideal for DIY audio projects & home audio systems.
Advantages & Disadvantages
The advantages of LM3876 IC include the following.
- LM3876 IC has an outstanding S/N ratio.
- It has a wide voltage supply range.
- This IC delivers c 56W of average power to a load.
- It has a 95 decibels minimum S/N ratio.
- This IC is an effective and handy audio amplifier chip.
- It has 0.06% THD+N at the rated output.
- This IC has 0.004% IMD.
- This IC has SOA (Safe Operating Area) that guards it from thermal runaway, under-voltage, overvoltage, overloads, etc.
- This IC has SPiKe protection that safeguards it from instant temperature peaks.
- Its performance is high.
- It is a good & stable IC.
The disadvantages of LM3875 IC include the following.
- This IC is useful for only 8-ohm loads.
- These amplifier ICs are noisy for very low listening levels.
- This IC may get heat whenever used hard.
- Its feedback compensation network reduces its slew rate.
- It must be derated whenever it operates at above 25°C case temperatures.
Applications
The applications of LM3876 IC include the following.
- Audio power amplifiers, self-powered speakers, component stereos, and similar devices utilize the LM3876 IC.
- This power operational amplifier serves audio applications and manufacturers can incorporate it into high-end stereo TVs.
- Its audio power amplifier delivers 56 watts of continuous average power to an 8ohms load with THD+N 0.1% from 20Hz to 20kHz.
- Its applications include compact stereo, component stereo, self-powered speakers, surround systems, etc.
- This power-operational amplifier serves audio applications and can be utilized in high-end stereo TVs.
Please refer to this link for the LM3876 IC Datasheet.
Thus, this is an overview of LM3876 IC, pinout, features, specifications, and applications. The LM3876 IC is a high-performance audio power amplifier that delivers 56 watts of power. So this power amplifier has a protection circuit to protect it. It maintains an excellent >95dB S/N ratio with a 2.0µV typical low noise floor. This IC exhibits 0.06% very low THD+N values over the audio spectrum at the rated o/p into the rated load. It provides outstanding linearity with a 0.004% IMD typical rating. Here is a question for you, what is LM383 IC?