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LM1875 general description:

LM1875 pcb layout
LM1875 pcb layout
The LM1875 is a monolithic power amplifier offering very low distortion and high quality performance for consumer audio applications. The LM1875 delivers 20 watts into a 4Ω or 8Ω load on ±25V supplies. Using an 8Ω load and ±30V supplies, over 30 watts of power may be delivered. The amplifier is designed to operate with a minimum of external components. Device overload protection consists of both internal current limit and thermal shutdown.The LM1875 design takes advantage of advanced circuit techniques and processing to achieve extremely low distortion levels even at high output power levels. Other outstanding features include high gain, fast slew rate and a wide power bandwidth, large output voltage swing, high current capability, and a very wide supply range. The amplifier is internally compensated and stable for gains of 10 or greater.

LM1875 amplifier circuit:


LM1875 power supply diagram:

LM1875 power supply diagram
LM1875 power supply diagram

LM1875 pcb layout:

LM1875 pcb layout
LM1875 pcb layout

LM1875 project review:

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100W Guitar Amplifier Schematic

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TDA8947J Audio Amplifier 29W

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TDA8947J general description:

The TDA8947J contains four identical audio power amplifiers. The TDA8947J can be used as: four Single-Ended (SE) channels with a fixed gain of 26 dB, two times Bridge-Tied Load (BTL) channels with a fixed gain of 32 dB or two times SE channels (26 dB gain) plus one BTL channel (32 dB gain) operating as a 2.1 system The TDA8947J comes in a 17-pin Dil-Bent-Sil (DBS) power package. The TDA8947J is pin compatible with the TDA8944AJ and TDA8946AJ. The TDA8947J contains a unique protection circuit that is solely based on multiple temperature measurements inside the chip. This gives maximum output power for all supply voltages and load conditions with no unnecessary audio holes. Almost any supply voltage and load impedance combination can be made as long as thermal boundary

conditions (number of channels used, external heatsink and ambient temperature) allow it.

TDA8947J features:

  • SE: 1 W to 25 W, BTL: 4 W to 50 W operation possibility (2.1 system)
  • Soft clipping
  • Standby and Mute mode
  • No on/off switching plops
  • Low standby current
  • High supply voltage ripple rejection
  • Outputs short-circuit protected to ground, supply and across the load
  • Thermally protected
  • Pin compatible with TDA8944AJ and TDA8946AJ

TDA8947J applications:

  • Television
  • PC speakers
  • Boom box
  • Mini and micro audio receivers

TDA8947J amplifier diagram:

TDA8947J layout:

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LX1720 Audio Amplifier 2x20W

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LX1720 general description:

The LX1720 controller IC contains the necessary functions to implement a stereo Class-D audio amplifier. A Class-D amplifier is a "switching" amplifier that converts a low-level, analog, audio input signal into a highpower, pulse-width modulated (PWM) output. The switching frequency is much higher than the audio band which allows high frequency out-of-band components to be removed with a simple LC filter. The LX1720 generates a PWM output by controlling external MOSFET's connected in a full-bridge configuration. Because the MOSFET's are either full "on" or full "off", their power dissipation is minimal allowing maximum power to be delivered to the speaker.

LX1720 Circuit:

LX1720 Audio Amplifier 2x20W
LX1720 Audio Amplifier 2x20W



TDA8922 Audio Amplifier 2x25W


TDA8922 general description:

The TDA8922 is a high efficiency class-D audio power amplifier with very low dissipation. The typical output power is 2 × 25 W. The device is available in the HSOP24 power package with a small internal heatsink and in the DBS23P through-hole power package. Depending on the supply voltage and load conditions, a very small or even no external heatsink is required. The amplifier operates over a wide supply voltage range from ±12.5 to ±30 V and consumes a very low quiescent current.

TDA8922 features:

  • High efficiency (∼90%)
  • Operating supply voltage from ±12.5 to ±30 V
  • Very low quiescent current
  • Low distortion
  • Usable as a stereo Single-Ended (SE) amplifier or as amono amplifier in Bridge-Tied Load (BTL)
  • Fixed gain of 30 dB in Single-Ended (SE) and 36 dB in
  • Bridge-Tied Load (BTL)
  • High output power
  • Good ripple rejection
  • Internal switching frequency can be overruled by an external clock
  • No switch-on or switch-off plop noise
  • Short-circuit proof across load and to supply lines
  • Electrostatic discharge protection
  • Thermally protected.

TDA8922 applications:

  • Television sets
  • Home-sound sets
  • Multimedia systems
  • All mains fed audio systems
  • Car audio (boosters).

TDA8922 amplifier diagram, circuit:

TDA8922 pcb layout:



LM3886 Audio Amplifier 1 x 108W


LM3886 general description:

According to National Semiconductor, the LM3886 is a high performance 150W Audio Power Amplifier with Mute. The performance of the LM3886, say NS, utilizing its Self Peak Instantaneous Temperature (°Ke) (SPIKe) protection circuitry, puts in a class above discrete and hybrid amplifiers by providing an inherently, dynamically protected Safe Operating Area (SOA). The LM3886T comes in an 11 (staggered-) lead non-isolated TO220 package.
We put the LM3886T schematic and an existing printed circuit board as a basis. For test purposes, the prototype of the amplifier was powered by a stabilized ±35-V supply. A maximum undistorted output power of about 63 watts into 8 ohms was obtained at a drive level of 1 Vrms. Dropping the load impedance to 4 ohms pushed the output power to no less than 108 watts. In practice, these power levels can be taken to mean ‘music power’, but do remember that the amplifier will not normally be powered from a regulated supply!

Great attention should be paid to the cooling of the amplifier IC. The cooling capacity offered by a heatsink as specified in the parts list is really only sufficient for load impedances of 6 ohms or more. Even if a heatsink with a thermal resistance lower than 1 K/W is employed, the amplifier IC will cause a ‘hot spot’ on the heatsink surface where the actual thermal resistance is much higher locally than the specification! With this in mind, it is recommended to drop the supply voltage to about ±30 V if the amplifier is used to drive a 4-ohm load. Also, bear in mind that heatsink isolating materials like mica and even ceramics tend to raise the thermal resistance by 0.2 K/W to 0.4 K/W. The metal tab at the back of the IC is at the negative supply potential.

Boucherot network C6-R6 is not normally required in this application, and should be omitted unless the amplifier is found to be unstable as a result of an application which is widely different from the one shown here. Populating the amplifier board itself will be a piece of cake, and most of the time required to build the amplifier will go into drilling, cutting, mounting and isolating the heatsink. Note that the radial electrolytic capacitors are rated at 40 volts, so you have to make sure that the supply voltage can never exceed that level. The performance of the prototype amplifier built and tested in our design lab is expressed by the Specifications box.

LM3886 circuit diagram:

LM3886 circuit diagram

LM3886 layout, pcb:

LM3886 layout and pcb

LM3886 part list:

LM3886 partlist

Datasheet for LM3886: Download


TDA7490 Audio Amplifier 2x25W

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TDA7490 general description:

The TDA7490 is a dual audio class D amplifier assembled in Flexiwatt 25 package; it is specially designed for high efficiency application mainly for TV and Home Stereo sets.

TDA7490 features: 

  • 25W + 25W OUTPUT POWER:
  • RL = 8Ω/4Ω; THD = 10%
  • ±10 TO ±25V)

TDA7490 amplifier diagram, circuits:

TDA7490 Audio Amplifier 2x25W
TDA7490 Audio Amplifier 2x25W

TDA7490 layout, pcb:

TDA7490 layout, pcb
TDA7490 layout, pcb

TDA7490 layout, pcb
TDA7490 layout, pcb




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General Description:

The TDA1908 is a monolithic integrated circuit in 12 lead quad in-line plastic package intended for low frequency power applications.The mounting is compatible with the old types TBA800, TBA810S, TCA830S and TCA940N. Its main features are:


  • flexibility in use with a max output curent of 3A and an operating supply voltage range of 4V to 30V;
  • protection against chip overtemperature;
  • soft limiting in saturation conditions;
  • low ”switch-on” noise;
  • low number of external components;
  • high supply voltage rejection;

Circuit Diagram



TDA7294 Audio Amplifier 2 x 80W

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TDA7294 general description:
This circuit described here uses two cis tda 7294 for use in stereo (2 x 80Watts) or bridge mode (1x 180 Watts), to configure this setting just four jumpers. To facilitate mounting the circuit has power supply attached. The power is kind of simple symmetrical with a bridge rectifier 6A, and two large electrolytic capacitors , 10000μF the 22000μF/50v. This Power supply will for the two modules. The processor is recommended 22-0-22 to 28-0-28 / 5A, depending on the quality of the transformer is recommended at least 6 amps of current.

TDA7294 features:
  • High power performances with limited supply voltage level.
  • Considerably high output power even with high load values (i.e. 16 Ohm).
  • Rl= 8 Ohm, 
  • Vs = ±25V 
  • Pmax = 150 W
  • Rl=16Ohm, 
  • Vs = ±35V 

TDA7294 circuit diagram:
TDA7294 circuit diagram

TDA7294 layout:
TDA7294 layout
TDA7294 pcb:
TDA7294 pcb

Datasheet for TDA7294: Download

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