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How to Design an Operational Schematic Amplifier

If you are an audiophile, musician or even just an electronics hobbyist, you should know how to design your own amplifier circuit. The amplifier is an important component of radios, many musical instruments and sound systems. While commercial amplifiers are readily available, many people like to make their own amplifiers so that they can customize the quality of sound that they produce. Before you can build your own amplifier, you need to be able to design a practical operational schematic.

Things You'll Need

Calculator

Instructions

- 1
  Divide your supply voltage by the maximum collector current for which your transistor is rated. The result is the sum of the emitter resistance and the collector resistance.
- 2
  Multiply the intrinsic resistance of your transistor by 20. This is a value for the emitter resistance that will ensure good temperature stability at room temperature.
- 3
  Subtract the emitter resistance from the sum of the emitter and collector resistances. The result is the collector resistance you need to keep the collector current within safe limits at the level of stability you have selected.
- 4
  Divide the collector resistance by the emitter resistance. If the result is higher than the gain you wanted, choose a higher emitter resistance and subtract it from the sum of the emitter and collector resistances to get a new collector resistance value. If the result is lower than the gain you wanted, then you will have to choose a lower emitter resistance. However, the lower the emitter resistance, the less stable its behavior will be. If you cannot find a good compromise between gain and temperature stability, then you need to find a new transistor, with different characteristics.
- 5
  Divide the maximum collector current by two and multiply the result by the emitter resistance. Add 0.6 to the result. This result is the voltage you need at the base of the transistor. Divide it by your supply voltage. Label this result ̶0;A.̶1;
- 6
  Divide the supply voltage by 10. Then divide the result by half of your transistor̵7;s maximum collector current. Then multiply this result by your transistor̵7;s beta value. Label this result ̶0;B.̶1;
- 7
  Multiply A by B. This result is the value you need for resistor one. Subtract this resistance from B. This result is the value you need for resistor two.
- 8
  Divide the value of resistor one into the number one. Label this result ̶0;C.̶1; Divide the value of resistor two into one. Label this result ̶0;D.̶1; Divide the value of the transistor̵7;s input resistance. Label the result ̶0;E.̶1; Add C, D and E together. Label this result ̶0;F.̶1;
- 9
  Multiply 6.18 by the lowest frequency to which you want your amplifier to respond. Label the result ̶0;G.̶1; Divide F by G. The result is the value that you need for capacitor one.
- 10
  Multiply the resistance of the device that you are hooking up to the amplifier̵7;s output by the lowest frequency to which you want the amplifier to respond. Multiply the result by 6.28. Divide the result of this into the number one. This final result is the value you need for capacitor two.
- 11
  Multiply the emitter resistance by the lowest frequency to which you wish your amplifier to respond. Multiply the result by 6.28. Divide the result into the number one. Multiply this result by 100. This final result is the value you need for capacitor three.

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