Bridging transistors

Hi! Title might seems confusing but I want to connect two seperate transistors' outputs - bridging them.

Main question: Would there be a short circut if I connect +V(voltage from another transistor output) to transistor output (Emiter if NPN, Collector is PNP)?

I didn't have such a problem with briding relays but now Im confused. Thanks in advance

by MateuszX
June 22, 2020

As shown, I don't see a possibility to have a short. On the other hand, if BOTH are turned ON, one of them will probably get warmer than the other (due to difference in the fabrication) and so, will conduct better, getting more current, getting warmer, getting more current... (thermal runaway). That is a reason why we don't often see bi-polar transistors in parallel. You should select the transistors such that ONE transistor could handle ALL the current by itself (including power dissipation considerations).

by vanderghast
June 24, 2020

This circuit is shown with one transistor on and the other off so it should be a case of either tr on lights both LEDs and I don't see a problem. If both are on for an appreciable time (overlap) then vandergast's comments apply. However you would normally have a resistor in series with each LED and this would improve load sharing in case of overlap.

by Foxx
June 24, 2020
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