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.
- Power Supply
- Pin 7 is connected to positive voltage (+9V).
- Pin 4 is connected to negative voltage (-9V).
- Ground: Pin 3 is connected to ground.
- Feedback Resistor: The feedback resistor connects Pin 2 to Pin 6.
- Input (Music Source)
- One input from the music player is connected to ground.
- The other input from the music player is connected to the input resistor (brown-black-red).
- The second lead of the input resistor is connected to Pin 2 of the op amp.
- Output (Speaker)
- One lead from the speaker is connected to Pin 6 of the op amp.
- 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.
- Feedback Resistor: Remove the feedback resistor that connected Pin 2 to Pin 6.
- Output (Speaker): Remove the connection between Pin 6 and the speaker.
Then make the following connections:
- 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.
- Transistor Power Supply
- Connect Pin 2 (base) of the TIP 122 transistor to the positive (+9V) power supply.
- Then connect Pin 2 (base) of the TIP 127 transistor to the negative (-9V) power supply.
- Output to Speaker
- Connect Pin 3 (emitter) of each transistor to a common output point on the breadboard.
- Then connect the output of the two transistor to one wire of the speaker.
- The other wire of the speaker should already be connected to ground.
- Feedback Resistor
- Connect one end of the feedback resistor to Pin 2 of the op amp.
- 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).