Analysing Op Amp Circuit with a Photo diode

In summary, the conversation discussed a circuit that was built for a lab. It involved using a photo diode to receive a blinking signal, which was then made visible on a DVM by an op amp. The use of negative feedback with a resistor was explained as a way to control the gain of the circuit. The purpose of the capacitors attached to the power rail was questioned, but it was later explained that they serve to clean up the power supply and reduce noise in high gain circuits. The term "bypass capacitors" was mentioned as a possible explanation for their use.
  • #1
zimbabwe
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For a lab we built the following circuit.

DiodeCircuit.jpg

Our photo diode was receiving a blinking signal which our op amp made visible on a DVM.

I do not understand the purpose of the capacitors attached to the power rail.
So far I understand how negative feed back with the Rf resistor controls the amount of gain. Without negative feed back the op amp would produce near infinite gain. The maximum voltage that can come out of the op amp is + or - 12V but about the capacitors I am at a loss.
Any help would be appreciated.
 
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  • #2
If you were using 12 volt batteries for your power supply the capacitors wouldn't serve any purpose. However power supplies connected to the mains have ripple and other noise, particularly switching supplies. With high gain circuits these imperfections are amplified and degrade the output. Those capacitors help clean up the power supply for the circuit.
 
  • #3
Thank you skeptic2.

I just came across the word bypass capacitors that must be it.
 

1. How does a photo diode work in an op amp circuit?

A photo diode is a type of diode that converts light energy into electrical energy. In an op amp circuit, the photo diode is connected in a feedback loop, where the current generated by the diode is amplified by the op amp. This allows for the detection and measurement of light levels in the circuit.

2. What is the purpose of using a photo diode in an op amp circuit?

The photo diode in an op amp circuit allows for the detection and measurement of light levels. This can be useful in applications such as light sensors, optical communication, and solar energy systems.

3. How does the gain of the op amp affect the performance of the photo diode in the circuit?

The gain of the op amp determines how much the output voltage will change in response to a change in the input voltage. In an op amp circuit with a photo diode, increasing the gain can improve the sensitivity and accuracy of the light measurement.

4. Can a photo diode be used in both inverting and non-inverting op amp configurations?

Yes, a photo diode can be used in both inverting and non-inverting configurations. In the inverting configuration, the diode is connected between the inverting input and the output of the op amp. In the non-inverting configuration, the diode is connected between the non-inverting input and ground.

5. How can the performance of a photo diode in an op amp circuit be optimized?

There are a few ways to optimize the performance of a photo diode in an op amp circuit. These include choosing an op amp with a high gain, using a low-noise power supply, and minimizing the distance between the diode and the op amp to reduce noise and interference. Additionally, using a high-quality photo diode and ensuring proper shielding and grounding can also improve performance.

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