Basic Amplifier Circuits

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Basic Amplifier Circuit for the LM714 Op Amp

Note: Pin 1 on the op amp is indicated by a small circular depression above that pin.

  1. Power Supply
    1. Pin 7 is connected to positive voltage (+9V).
    2. Pin 4 is connected to negative voltage (-9V).
  2. Ground: Pin 3 is connected to ground.
  3. Feedback Resistor: The feedback resistor connects Pin 2 to Pin 6.
  4. Input (Music Source)
    1. One input from the music player is connected to ground.
    2. The other input from the music player is connected to the input resistor (brown-black-red).
    3. The second lead of the input resistor is connected to Pin 2 of the op amp.
  5. Output (Speaker)
    1. One lead from the speaker is connected to Pin 6 of the op amp.
    2. The other lead of the speaker is connected to ground.

 

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  Op Amp Circuit Enhanced with Transistors

 

 

 

 

 

 

To enhance the basic op amp circuit, begin by temporarily removing the feedback resistor and the output connections to the speaker from the circuit.

  1. Feedback Resistor: Remove the feedback resistor that connected Pin 2 to Pin 6.
  2. Output (Speaker): Remove the connection between Pin 6 and the speaker.

Then make the following connections:

  1. Connect the Transistor Collectors to the Op Amp Output:

Connect Pin 1 (collector) of each of the two transistors to Pin 6 (output) of the op amp.

  1. Transistor Power Supply
  2. Connect Pin 2 (base) of the TIP 122 transistor to the positive (+9V) power supply.
  3. Then connect Pin 2 (base) of the TIP 127 transistor to the negative (-9V) power supply.
  1. Output to Speaker
  2. Connect Pin 3 (emitter) of each transistor to a common output point on the breadboard.
  3. Then connect the output of the two transistor to one wire of the speaker.
  4. The other wire of the speaker should already be connected to ground.
  1. Feedback Resistor
  2. Connect one end of the feedback resistor to Pin 2 of the op amp.
  3. Connect the other end of the feedback resistor to the common output point (that, in turn, is connected to the speaker) described in Step 3 (above).