1. What is Intrinsic Stand-off Ratio?

The Intrinsic Stand-off Ratio (η) for UJT (Unijunction Transistor) based thyristor firing circuits is defined as the ratio of emitter base 1 resistance to the total emitter base junctions resistances. It is a crucial parameter in determining the firing characteristics of UJT circuits.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( \eta \) — Intrinsic Stand-off Ratio
• \( R_{B1} \) — Emitter resistance base 1 (Ω)
• \( R_{B2} \) — Emitter resistance base 2 (Ω)

Explanation: This ratio determines the voltage division between the two base terminals and affects the triggering point of the UJT in thyristor firing circuits.

3. Importance of Intrinsic Stand-off Ratio

Details: The intrinsic stand-off ratio is critical in UJT-based oscillator circuits and thyristor firing circuits as it determines the peak point voltage and thus controls the firing angle of the thyristor.

4. Using the Calculator

Tips: Enter the resistance values for R_B1 and R_B2 in ohms. Both values must be positive and greater than zero for accurate calculation.

5. Frequently Asked Questions (FAQ)

Q1: What is the typical range of intrinsic stand-off ratio?
A: The intrinsic stand-off ratio typically ranges from 0.5 to 0.8 for most UJT devices.

Q2: How does the stand-off ratio affect thyristor firing?
A: A higher stand-off ratio results in a higher peak point voltage, which delays the firing of the thyristor, while a lower ratio advances the firing angle.

Q3: Can this calculator be used for all UJT types?
A: Yes, the formula is universal for all unijunction transistors, though specific UJTs may have slightly different characteristic ranges.

Q4: What are the units for resistance values?
A: Both R_B1 and R_B2 should be entered in ohms (Ω).

Q5: Is the stand-off ratio temperature dependent?
A: Yes, the intrinsic stand-off ratio may vary slightly with temperature, though the variation is typically small for most practical applications.