Photodiode parallel to a capacitor

In summary, the photodiode shows a current-to-voltage characteristic with a turn-on voltage, and receives irradiation for a given time. Once irradiated, a photocurrent flows and the capacitor starts charging. A positive voltage drop arises on the capacitor, with a sign so that the photodiode is forwardly biased. At a certain irradiation dose (i.e., after a certain irradiation time), the accumulated charge on the capacitor will produce a voltage drop > turn-on voltage, and a forward current will flow on the photodiode, so that voltage drop is limited by such a current. Once irradiation stops, the device keeps the photogenerated charge on the capacitor, but the
  • #1
arrenio
1
1
Dear Forum Members, I am looking for someone who can help me to model the behavior of a photodiode in parallel with a capacitor. I want to model the behavior of a device that I have developed.
As you can see in my attached file, the photodiode shows a current-to voltage characteristic with a turn-on voltage Vto, and receives irradiation for a given time tirr. The photodiode is connected in parallel with an ideal capacitor Cp. Once the photodiode is irradiated, a photocurrent Ip flows and the capacitor starts charging. A positive voltage drop Vac arises on the capacitor, with a sign so that the photodiode is forwardly biased. At a certain irradiation dose (i.e., after a certain irradiation time) the accumulated charge on the capacitor will produce a voltage drop > Vto, and a forward current will flow on the photodiode, so that voltage drop Vac is limited by such a current. Once irradiation stops, given the photodiode has a zero leakage current, the device keeps the photogenerated charge on the capacitor, but the behavior is not linear vs. irradiation time, due to the discharge of photogenerated charge above Vto.
Can someone help me in modeling such a behavior?
thank you!

schematic and experimental IV curve of the photodiode

Immagine1.png
Immagine2.png
 
Engineering news on Phys.org
  • #2
The diode (without illumination) does not follow the ideal diode behavior characterized by a turn-on voltage, but is more properly represented by the Schockley diode equation. The Schockley diode equation has a couple of parameters that can be input to adjust it for the particular diode at hand. Google "Schockley diode equation". Hopefully this is helpful. ..editing...I think you may already have the Schockley diode equation there. The diode equation looks very similar when there is light shining on it versus no light=the I-V curve shifts in the y-direction. There is no such thing as "no leakage current". The Schockley diode equation should provide you with a number for the "leakage current as a function of voltage...I think the origins of this leakage current are the result of thermally generated electrons in the "p" side of the photodiode, but you may want to research that further.
 
Last edited:

1. What is a photodiode parallel to a capacitor?

A photodiode parallel to a capacitor refers to a circuit configuration where a photodiode and a capacitor are connected in parallel to each other. This means that both components are connected to the same two nodes in the circuit.

2. How does a photodiode parallel to a capacitor work?

In this configuration, the photodiode acts as a current source, generating a current proportional to the amount of light it receives. The capacitor works as a storage component, storing the charge generated by the photodiode. This allows for a continuous flow of current, even when the light intensity fluctuates.

3. What are the applications of a photodiode parallel to a capacitor?

This configuration is commonly used in light sensing applications, such as in light meters, cameras, and optical sensors. It can also be used in circuitry for automatic exposure control, where the photodiode detects the level of light and adjusts the exposure accordingly.

4. What are the advantages of using a photodiode parallel to a capacitor?

One of the main advantages is the continuous flow of current, even with varying light levels. This makes it suitable for use in low light conditions. Additionally, this configuration is less susceptible to noise and interference, making it more accurate and reliable.

5. What are the limitations of a photodiode parallel to a capacitor?

One limitation is that the response time of the circuit may be slower compared to other configurations. This is due to the charging and discharging of the capacitor. Additionally, the accuracy of the circuit may be affected by temperature changes, as the properties of both the photodiode and capacitor can be affected by temperature.

Similar threads

PIN photodiode forward bias capacitance
    • Electrical Engineering
Replies
12
Views
3K
Solving the Debate Over Photon Counting With a Scintillation Device
    • Electrical Engineering
Replies
7
Views
2K
DC Blocking Capacitor: Solving a Photodiode Circuit Problem
    • Electrical Engineering
Replies
24
Views
3K
Can I use individual capacitor IR for parallel circuit balancing resistors?
    • Electrical Engineering
Replies
3
Views
1K
Resistive heating power AC vs rectified AC/DC
    • Electrical Engineering
Replies
10
Views
2K
Why Do Capacitors Behave Differently in Series and Parallel Configurations?
    • Introductory Physics Homework Help
Replies
20
Views
419
Understanding Capacitor Behavior for Noise Filtering?
    • Electrical Engineering
Replies
15
Views
3K
Question about the energy stored in an RLC parallel resonant network
    • Electrical Engineering
2
Replies
44
Views
3K
Relay and Capacitor circuit - blinking LED
    • Electrical Engineering
Replies
26
Views
4K
An inductor and a capacitor with a state
    • Electrical Engineering
Replies
1
Views
1K

Hot Threads

Recent Insights

Back
Top