[Serial Article] The wonderful characteristics of bipolar transistors that seem like they will disappear but won't disappear ~ Series 3: Emitter-base voltage Vebo

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Basic Analog Discrete Power Devices On Semi

Emitter-base voltage Vebo

In the third installment of this series, we will explain the emitter-base voltage Vebo.

The emitter-base junction breakdown voltage is generally in the range of 6V to 9V.
Since the junction is formed by a high-concentration diffusion layer, the breakdown voltage is low, as mentioned above.
Furthermore, since high-concentration EB junctions are easily destroyed, for example, when driving a motor with an NPN-NPN half-bridge configuration, care must be taken to ensure that the back EMF from the motor, or a voltage of Vebo or more, does not enter the high-side emitter.

When designing ICs in my previous job, we always addressed this issue by inserting a clamp diode between the emitter and collector.
As an aside, the damage to EB junctions often appears as clean stripes (see Figures 11 and 12), and since the characteristics are a simple diode operation, it is easy to determine whether or not there has been damage (see Figure 13).
Furthermore, the measures to prevent destruction are simple. I recommend that new engineers use an NPN in a switching power supply circuit or a motor drive circuit to intentionally destroy it and think about countermeasures.