Timeline for NPN and PNP Transistors. Does switching the transistors hard at it bases, how will it affect the transistors?
Current License: CC BY-SA 4.0
6 events
| when toggle format | what | by | license | comment | |
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| Oct 10, 2021 at 21:36 | comment | added | user57037 | When using a transistor as a saturated switch, the goal is usually to run the base at 1/20th or 1/10th of the desired collector current. This helps insure that Vce will be low. To say it another way, instead of assuming a gain of 100, assume a gain of 10 or 20 at the most. | |
| Oct 10, 2021 at 21:35 | comment | added | Citi | Yes, I used the transistors to implement a high side switch, I updated my question, keeping in mind the 1/10th collector current. I was wondering if someone can tell me if my worked values are good and understandable to use. thank you for your help | |
| Oct 10, 2021 at 16:00 | comment | added | Audioguru | The datasheet for every transistor shows that hFE is used when the transistor always has plenty of Vce as an amplifier. It shows a base current of 1/10th the collector current (regardless of hFE) when the transistor is used as a saturated switch because then the Vce is very low. | |
| Oct 10, 2021 at 15:56 | comment | added | The Photon | @Citi, if you're concerned about the power contribution from the base current, consider just using a MOSFET instead of a BJT. | |
| Oct 10, 2021 at 5:37 | comment | added | Citi | Thank you for your answer. I see how allowing more current at the base is not really driving hard. Yes, what I'm concern about is that using low resistor values at its bases will affect the power dissipation. I only need at least 100ma at the PNP Ic current, so I might change the resistor values to R1=10k and R=4.7K | |
| Oct 10, 2021 at 3:54 | history | answered | kalyanswaroop | CC BY-SA 4.0 |