What is a Class A Amplifier?

The Class A amplifier is the type of the simplest form of a power amplifier which can be used as a single switching transistor in the standard common emitter circuit configuration to produce an inverted output from a given signal.

Required materials/components to build this circuit 

  • A B688 Transistor
  • A Heat Sink
  • 1K Resistor
  • Terminal block
  • Toroidal Coil

The above picture shows a physical description  of the B688 Transistor.

Steps for making the Amplifier Circuit 

  • First, a total of 6 Transistors as mentioned above has to be arranged in a linear format on the top of the heat sink as shown in the following figure.

  • And the common terminals of the Transistors have to be shorted through the wire as shown in the figure. (all the emitters have to be shorted, all the collectors will also be shorted and also all the bases have to be shorted as shown above)
  • And the resistor and the capacitor will have also been joined according to the following figure and the volume control (POT) and the terminal block has also been arranged in the below figure.

  • Then a toroidal coil will have to be placed in the base of the heat sink as shown in the below picture.

  • So the finally assembled circuit for the amplifier should look like below.

Now the circuit is ready to be connected with an external speaker for the amplification operations and this is how the circuit is made.

Some Basics about the Transistor action

We know that The transistor is a semiconductor device that can both conduct and insulate. A transistor can be used as a switch and an amplifier. It converts audio waves into electronic waves and resistors while controlling electric current. Transistors have a very long life, and it is smaller in size, can operate on lower voltage and also supplies for greater safety, and also requires no filament current. The first transistor was fabricated with germanium material instead of silicon. It is the fundamental building block of modern electronic devices and also found everywhere in modern electronic systems.

Biasing is here referred to provide resistors, capacitors, or supply voltage and also to provide proper operating characteristics of the transistors. DC biasing is used mainly to obtain the DC collector current at a particular collector voltage of the transistor. The value of these voltages and currents are expressed in terms of  Q-Point which is a great measure of the transistor. In a transistor amplifier configuration, the IC (max) is the maximum current in the transistor and VCE (max) is the maximum voltage applied across the transistor. To work with the transistor as an amplifier, a load resistor RC must be connected to the collector for the load management and safe operation.


So we have discussed the amplifier action and use of the B688 Transistor as an amplifier and also the steps for building the entire circuit is also described above, make the circuit and enjoy the analog technologies, for buying components at very low prices please visit UTSource.net