These terms are not entirely clear to me, so analyzing the results of my simulations would be problematic.
Your understanding of the terms is on the right track, but let's clarify them further and then talk about how you might interpret the results of your simulations.
1. Saturation Current (IS):
What is it?
The saturation current, (I_S), represents the reverse-biased current that flows due to minority carriers in the semiconductor. It's a tiny current, often in the nano or picoampere range, and is present even in the absence of external voltage because of thermal energy.
In Zener Diodes:
While (I_S) is more commonly associated with the Shockley diode equation for regular diodes in forward bias, in the context of a Zener diode, increasing (I_S) might mean a larger 'leakage' or 'minority carrier' current before breakdown.
2. Emission Coefficient (N):
What is it?
The emission coefficient, (N), often termed the ideality factor, determines how closely the diode follows the ideal diode equation. A value of (N = 1) suggests ideal diode behavior, while values > 1 suggest some non-idealities due to recombination, generation, or tunneling processes.
In Zener Diodes:
For Zener diodes, the value of (N) typically affects the forward-biased behavior more than the reverse breakdown. A larger (N) can mean a softer knee in the forward I-V curve.
3. Breakdown Voltage (BV):
What is it?
Breakdown voltage, (BV), is the reverse voltage at which the diode starts conducting a significant reverse current. For Zener diodes, this is the voltage at which the Zener effect (or avalanche breakdown for higher voltage Zeners) takes place.
In Zener Diodes:
The Zener voltage is the key specification for a Zener diode. It's the voltage at which you get a sharp rise in reverse current.
Interpreting Simulation Results:
Varying IS:
- If you increase (I_S), expect to see a slight increase in reverse current before reaching the Zener breakdown. However, the primary Zener breakdown behavior might not change dramatically.
Varying N:
- As you change (N), the forward-biased behavior of the Zener diode will be more affected than the reverse breakdown. A larger (N) might result in a softer forward knee in the I-V curve.
Varying BV:
- Changing (BV) directly impacts the reverse breakdown voltage. A Zener diode with a higher (BV) will start conducting significant reverse current at a higher reverse voltage.
In conclusion, to analyze your simulation results:
Plot I-V Curves: Look at both forward and reverse bias. Notice how the knee of the curve changes with (N) and how the reverse breakdown shifts with (BV).
Examine Breakdown Behavior: Observe the exact voltage at which the diode goes into breakdown for different (BV) values.
Check Forward Bias: Although Zener diodes are primarily used for their reverse bias properties, it's still instructive to look at the forward bias behavior, especially when you vary (N).
Remember, while the SPICE model captures a lot of the diode's behavior, real-world characteristics like temperature dependence, noise, and device-to-device variations might not be fully represented. Always cross-check with datasheets when designing real-world circuits.
