UJT peak-point condition with interbase bias A unijunction transistor (UJT) has an interbase voltage VBB applied. What is the emitter voltage at the peak point?

Introduction / Context:
The UJT is widely used for triggering, relaxation oscillators, and timing circuits. Its operation hinges on the intrinsic standoff ratio, usually denoted by η (here shown as h), which sets the peak-point voltage at which the device switches into its negative-resistance region.

Given Data / Assumptions:

• Interbase bias VBB is applied between B2 and B1.
• η (written as h in the options) is the intrinsic standoff ratio (0.5–0.8 typically).
• VD is the forward diode drop of the emitter junction (about 0.2–0.7 V depending on device).

Concept / Approach:
The well-known UJT peak-point relation is VP = η * VBB + VD. Physically, as the emitter voltage rises and equals the potential at the emitter junction plus the diode drop, the device conducts strongly and its dynamic resistance becomes negative, enabling sawtooth generation in relaxation circuits.

Step-by-Step Solution:
Write the peak-point formula: V_P = η * VBB + V_D.Identify symbols in options: η ≡ h; therefore V_P = hVBB + VD.Select matching option accordingly.

Verification / Alternative check:
Check a typical UJT datasheet or textbook: the same formula is quoted and used for design of timing networks.

Why Other Options Are Wrong:

• hVBB omits the diode drop term.
• (h + 1) VBB is dimensionally incorrect and not standard.
• VD alone ignores the standoff partitioning.
• VBB − VD is unrelated to the internal resistive divider physics.

Common Pitfalls:

• Assuming VD is negligible; it matters at low VBB values.
• Confusing η with a fixed 0.5; it varies by device.

Final Answer:
hVBB + VD