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LM1875 Datasheet – 25W HIFi audio amplifier circuit

Here is an LM1875 datasheet, used for a 20W audio amplifier on Class AB type. Voltage Gain is 90dB. Low Harmonic Distortion Noise is 0.015%, 1KHz, 8 ohms. and Wide supply range 16V-60V at 4A. Protection for short circuits to ground and thermal shutdown.

General Description

The LM1875 is used on a wide power amplifiers very low distortion and high-quality efficiency for audio applications. It provides power is 20 watts into a 4 ohms or 8 ohms load on 25V supplies.

Its amplifiers circuits are designed to working with a minimum of external parts.

When overload it has protection consists of both internal current limit and thermal shutdown.

Other features are high gain, fast slew rate and a wide bandwidth, large output voltage swing, high current capability, and a very wide supply range. See below.


In the Figure 1 as Connection Diagram and Typical Applications of LM1875

The amplifier is internally compensated and stable for gains of 10 or greater.

Specification Value
– Up to 30 watts / channel output power
– Maximum Load Resistance: 4 to 8 Ohm
-Maximum Input Bias Current : [email protected]±25V
– Maximum Input Offset Voltage :[email protected]±25V
– Maximum Working Temp : 150°C
– Avo typically 90 dB.
– Low harmonic Distortion Noise : 0.015% @ 1KHz @ 8 ohms @ 20 watts.
– Wide power bandwidth: 70KHz
– High current capability: 4A.
– Maximum Supply Current : [email protected]±25V
– Wide supply range : 16V-60V

The Power supply type are single and dual, there is detail as follow.

-Minimum Single Supply Voltage: 16V
-Typical Single Supply Voltage: 18V|24V|28V
-Maximum Single Supply Voltage: 60V
-Minimum Dual Supply Voltage: ±8V
-Typical Dual Supply Voltage: ±9V|±12V|±15V|±18V|±24V|±28V
-Maximum Dual Supply Voltage: ±30V
– 94dB ripple rejection
– Typical Gain Bandwidth Product 5.5MHz
– Typical Supply Current: 70mA at ±25V
– Protection for AC and DC short circuits to ground
– Thermal protection with parole circuit.
– Internal output protection diodes.
– Plastic power package: TO-220

We use it’s on the High-performance audio systems, Bridge amplifiers, Stereo phonographs, Servo amplifiers, Instrument systems and more.

25W Hi-Fi Audio Amplifier using ic LM1875

This circuit is the audio amplifier circuit has a very popular one.This is a simple circuit. Small pieces of equipment. And Watt is high.The circuit uses IC number LM1875, which is under the protection circuit IC output or Too short circuit. And a significant distortion as low as 0.015% at a frequency of 1kHz.

25W HI-FI power amplifier using LM1875

This circuit uses positive, negative ground power supply to get the audio signal with both halves of the signal swing, positive and negative halves, The sound that came out crystal clear.Work is. When paying for the audio input. Audio is through R1, R2, C1, and R3 to limit the audio signal appropriately.And limit the noise to the input signal mixed down to the ground.Then sends a signal to noise to the input pin of IC 1.A noninverting pin, amplifier non-return phase.Out of the 4 output pins to access the speakers.The R6 and C4 eliminate noise mixed with the output down to the ground.And another part of the audio output pin 4 of the integrated circuit will be fed back into place through R5 to pin 2, which R4 and R5 determine the rate of boost up, can be calculated from R5/R4, will gain equal to 15 times, With a C2 to meet high frequencies better.

This Post Has 4 Comments

  1. I was worried about the C4’s polatity…. I guess C4 in the schematics should be reversed. Correct me if i am wrong 🙂

    1. Hello, Lone Ranger
      Oops! I am very very sorry. I am so sad.
      You are right. I mistake.
      You are good. But I am too late. to check it.

      Thank you so much.

  2. lone ranger, you are right, + of c4 should be in the common terminal of the circuit since it’s a dual supply…

    1. Hi Princess,
      Yes, I mistake.
      Thank you so much.
      I hope you visit me again.

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