# Calculating Is and nVt for Silicon Diode, How?

• CDTOE
In summary, the conversation was about conducting a diode experiment to determine the values of nVt and saturation current (Is). The experiment involved connecting a DC power supply in series with a forward-biased silicon diode and a resistor, and taking voltage readings at different levels. The equation V2-V1=2.3nVt log(I2/I1) was used to calculate nVt, and the resulting value was then used in the equation I=Is e^(V/nVt) to calculate Is. It was suggested to take more than two readings on the I-V curve for a more accurate estimate of nVt. The values can be deduced from the typical V-I curve on the diode's
CDTOE
Hello, everyone!

I was asked by my lab instructor for an Electronic course to conduct a diode experiment by which I can get the value of (nVt) and saturation current (Is) for that diode.

I did the experiment by connecting a DC power supply in series with a forward-biased silicon diode (1N4007-MIC), and a 1Kohm resistor. I took voltage reading across the diode starting from 10V DC supply, down to 1V. Now, I have the readings, plus I calculated the diode current (ID) for each -1V difference in DC supply. Also, I graphed a curve of I-V characteristics.

Well, I understand that to get the value of nVt and Is, I have to take two values on that curve, an upper value of VD(V2) on the horizontal axis corresponding to an upper value of ID(I2) on the vertical axis, and a lower value of VD(V1) corresponding to a lower value of ID(I1). I take these values and substitute in the equation:

V2-V1=2.3nVt log(I2/I1) --> From this, I can calculate the only unknown value which is nVt.I take the resulting value and substitute in the equation:

I=Is e^(V/nVt) --> From this, I can calculate the only unknown value which is Is.

So, my question is, is my understanding to how to get the two values correct? is there any shorter and easier way to get them?

Also, where can I find the the two values in the diode's datasheet? I looked up for it but didn't find any indication of it (this datasheet for example).

Thanks.

Hi CDTOE! http://img96.imageshack.us/img96/5725/red5e5etimes5e5e45e5e25.gif

CDTOE said:
So, my question is, is my understanding to how to get the two values correct? is there any shorter and easier way to get them?
It looks fine. Take more than just 2 readings off the graph, and determine an average of your nVt estimates.

Also, where can I find the the two values in the diode's datasheet? I looked up for it but didn't find any indication of it (this datasheet for example).
You might have to deduce them from the typical V-I curve provided?

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## 1. How do you calculate the reverse saturation current (Is) for a silicon diode?

The reverse saturation current for a silicon diode can be calculated using the equation Is = A * T^3 * exp(-Eg/(kT)), where A is a constant (around 10^-12 A/cm^2), T is the temperature in Kelvin, Eg is the bandgap energy of silicon (1.12 eV), and k is Boltzmann's constant (8.62 x 10^-5 eV/K).

## 2. How do you calculate the thermal voltage (Vt) for a silicon diode?

The thermal voltage for a silicon diode can be calculated using the equation Vt = kT/q, where k is Boltzmann's constant, T is the temperature in Kelvin, and q is the electron charge (1.60 x 10^-19 C).

## 3. What is the significance of the reverse saturation current (Is) in a silicon diode?

The reverse saturation current (Is) in a silicon diode is a measure of the leakage current that flows through the diode when it is reverse biased. It is an important parameter in diode design as it can affect the performance and efficiency of the diode.

## 4. How does temperature affect the reverse saturation current (Is) in a silicon diode?

The reverse saturation current (Is) in a silicon diode increases with increasing temperature. This is because as temperature increases, more electron-hole pairs are created in the diode, leading to a higher leakage current.

## 5. Can the thermal voltage (Vt) be used to determine the operating temperature of a silicon diode?

No, the thermal voltage (Vt) cannot be used to determine the operating temperature of a silicon diode. It is only a measure of the voltage equivalent to the thermal energy of an electron at a specific temperature. The operating temperature of a diode can be determined by measuring the forward voltage drop across the diode at a known current.

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