Problems caused by parallel transistor base

The problem here is that one control port supplies power to the bases of three PNP transistors. When one transistor fails, it cannot enter the saturation zone. Due to the different initial values of VBE and HFE for each transistor, which vary greatly with temperature changes, the three transistors cannot be biased correctly. The transistor with lower VBE has the highest bias resistance current, while the bias current of the other two transistors appears smaller.

If Ib is too small, assuming Ic is constant

In the case of H=Ic/Ib, it is easy to enter the amplification zone at low temperatures, causing Vce to be too large and potentially causing logical problems.

Therefore, even if an NPN can be used to bias several PNP transistors, each transistor should have an independent base resistance, which can achieve a certain current sharing through resistance in the presence of Vbe differences, ensuring current independence.

Even the control end cannot connect multiple pipes together casually, which is something we need to pay attention to.

Problems caused by parallel transistor base

The problem here is that one control port supplies power to the bases of three PNP transistors. When one transistor fails, it cannot enter the saturation zone. Due to the different initial values of VBE and HFE for each transistor, which vary greatly with temperature changes, the three transistors cannot be biased correctly. The transistor with lower VBE has the highest bias resistance current, while the bias current of the other two transistors appears smaller.

If Ib is too small, assuming Ic is constant

In the case of H=Ic/Ib, it is more likely to enter the amplification zone at low temperatures, causing Vce to be too large and potentially causing logical problems.

Therefore, even if an NPN can be used to bias several PNP transistors, each transistor should have an independent base resistance, which can achieve a certain current sharing through resistance in the presence of Vbe differences, ensuring current independence.

Even the control end cannot connect multiple pipes together casually, which is something we need to pay attention to.