1W AMPLIFIER WITH LM380N-8. Intercoms today are widely used in everyday life, but they have the drawback of not having enough output power to listen to them in noisy environments. For these cases, it is convenient to place an amplifierat the exit and achieve a good level of audio. The model we present has a power of 1 watt and is powered by a wide voltage range (between 9 and 15 Vdc); Its small size makes it easily adaptable to any cabinet. Or you can even mount it within the same intercom. Another important feature is that the integrated circuit (LM 380 type) does not need a heatsink, allowing it to be placed inside plastic cabinets. The input signal must have a voltage between 50 and 100 mV
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- 1 OPERATION
- 1 NOTE
- 2 ADJUSTMENT
- 3 LIST OF COMPONENTS
- 1 RESISTORS
- 2 CAPACITORS
- 3 SEMICONDUCTORS
- 4 ASSEMBLY NOTES
- 5 Sources
This circuit is built based on an LM380 N-8 integrated circuit, which is a single chip audio amplifier. The gain of this amplifier is fixed (34 db or 50 times) and is given by the construction of the IC. The input stage allows the ground to be used as a reference for the input signals; the integrated output is protected against short circuits. It also has an internal limitation against over temperatures. With the power supply between 9 and 15Vdc, the output power will vary between 0.8 and 1.5W without the need for a heatsink for the integrated circuit. For the amplifier to work properly, the input signal must have a voltage between 50 and 100 mV of effective value. C3 ( capacitor of bypass) avoid oscillations; The network of zobel composed of R2 and C5 makes the speaker reflect in the integrated as a pure resistance.
The resistance R1 must be the same value as the impedance of the circuit or antenna to be connected to the input.
This circuit only needs an adjustment to function properly. The input must be short-circuited and the 12 Vdc supply must be installed. Adjust R3 until a voltage of 1.5 Vdc is measured between the terminals of R2.
- R1 = 47 Kohms (Yellow-Violet-Orange)
- R2 = 2.7 ohms (Red-Violet-Gold)
- P1 = POTENTIOMETER 50 Kohms Logarithmic (not provided)
- C1 = C4 = 470 µF 25V (Electrolytic)
- C2 = C3 = 2.2 µF 25V (Electrolytic)
- C5 = 100 nF (Ceramic)
- IC1 = LM380N-8
- It is recommended to use shielded cable for the input connections and the potentiometer, connecting the meshes to ground.
- The speaker is 8 ohms 2W, because it is always necessary to oversize the power so that it does not break when placing the volume of the system at maximum.