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Certainly! A Classic 100W HiFi Darlington Transistor Amplifier Circuit is a popular design in the realm of audio amplifiers. The use of Darlington transistors allows for high gain, which is crucial for driving speakers with high fidelity.

Component Description:

  • Transistors: The transistors in the Darlington pair configuration are responsible for the amplification. Darlington pairs offer very high gain, making them suitable for audio amplification.
  • Resistors (R1-R6): These resistors are used to bias the transistors and set the operating point of the circuit. The values of these resistors can be calculated based on the desired operating conditions and the specifications of the transistors used.
  • To Speakers: The output of the amplifier is connected to the speakers. The positive and negative terminals of the speakers are connected to the collector of the respective transistors.

This particular 100W amplifier circuit, powered by a symmetrical 2x42V supply, provides a robust 100W RMS output. However, a word of caution: when driving your speaker, be mindful of the sound level. Although it can reach up to 140W, it’s essential to note that exceeding 100W RMS or 250W peak can lead to distortion. The author emphasizes the importance of understanding the power levels to ensure optimal performance.

Regarding the output transistors, the circuit calls for 1x ON709 and 1x BDX88C in TO3 packages. However, locating these specific transistors might be challenging. In such cases, the author suggests using T8 NPN transistors for BDW83C or TIP142 and T9 PNP transistors for BDW84C or TIP147, corresponding to SOT-93 package transistors. Additionally, for effective heat dissipation, a larger heatsink and a heat conductor, such as thermal paste, along with proper insulation, are recommended.

To set the rest current, the author advises connecting an ammeter between the T8 collector and the positive feed. Adjust the 10k trimpot until the ammeter reads 50mA, ensuring the amplifier operates within the specified parameters.

An ammeter is a device utilized to gauge electric current in a circuit, with measurements expressed in amperes, reflecting its name. In the process of direct measurement, the ammeter is integrated into the circuit, aligning with the current to be assessed.

Ammeters, designed for measuring both direct (DC) and alternating (AC) electric current in amperes, boast a wide measurement range. This breadth is achievable because, particularly at high values, only a fraction of the current passes through the meter mechanism; a parallel shunt takes on the bulk of the current load.

Electric current, quantified by an ammeter, employs diverse measurement methods and units. The SI unit for current is the Ampere, or Amp. Ampere quantifies the flow of electric charge across a surface over one coulomb per second. The underlying principle of an ammeter necessitates low opposition and inductive reactance. This leads to a low impedance design, ensuring minimal voltage drop across the ammeter.


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