What occurs if voltage exceeding the absolute maximum rated emitter-base voltage is applied to the base terminal?

Do not apply a voltage exceeding the rated emitter-base voltage (V_EBO) shown in the Absolute Maximum Ratings table (Table 1) to the base terminal (negative bias in the case of npn transistors and positive bias in the case of pnp transistors). Doing so will degrade h_FE and other parameters.

When a monostable multivibrator is composed of bipolar transistors, a bias voltage exceeding the rated V_EBO might be applied to the base.

The following describes the operation of the multivibrator shown in Figure 1.

1.Suppose that Q₁ is initially on. Therefore, the collector voltage of Q₁ is close to the GND level.
C₁ is charged via R₃ while C₂ is charged via R₂.

2.As C₁ is charged, the base-collector voltage of Q₂ reaches its turn-on voltage (roughly 0.7 V), turning it on.
The collector voltage of Q₂ drops to a level close to GND. Immediately before this point, the voltage across C₂ is charged at V_CC – 0.7 V. Even when the collector voltage of Q₂ drops, C₂ remains charged. Therefore, the voltage at the C₂ terminal on the base side of Q₁ drops to 0.7 V – V_CC.

These steps are repeated to act as a monostable multivibrator.

Suppose that V_CC = 10 V. Then, the emitter-base voltage of Q₁ and Q₂ reaches -9.3 V, exceeding the rated V_EBO of -5 V.