Pre-biased transistor

[MarkR42]

Hi,

Yesterday I learned that pre-biased transistors are a thing.

For example this one: https://lcsc.com/product-detail/Digital-Transistors_ON-Semiconductor-ON-MUN2212T1G_C274587.html

Surely they are ideal for low-side switching of small loads from e.g. a microcontroller? It avoids the extra resistor(s).

Has anyone tried them (or similar)? Did it work as expected?

[Paul Rose]

Surely they are ideal for low-side switching of small loads from e.g. a microcontroller? It avoids the extra resistor(s).

Yep.  That's what they're good for.  Work fine.

[Mechatrommer]

Hi,
Yesterday I learned that pre-biased transistors are a thing.
For example this one: https://lcsc.com/product-detail/Digital-Transistors_ON-Semiconductor-ON-MUN2212T1G_C274587.html
Surely they are ideal for low-side switching of small loads from e.g. a microcontroller? It avoids the extra resistor(s).
Has anyone tried them (or similar)? Did it work as expected?

seems like more suitable for driver for the next stage's analog amplifier such as darlington or RF amp maybe. for direct driving load from mcu, n-mosfet such as AO3400 is better ymmv.

[Paul Rose]

I think the fact that the link and data sheet call them "digital transistors" is a hint at their anticipated use case.  Though I agree that I might typically reach for a mosfet.

[Kleinstein]

The digital transistor compete with small MOSFETs, like 2N7002 , BSS138 and similar. They may be a little cheaper and lower ESD sensitivity and sill good enough to drive a LED. With a BJT the turn on level is also better defined than with MOSFETs. With a very low signal level this can be an issue.

[Benta]

Logic-level MOSFET or BJT (in this case BRT, bias-resistor transistor) is a question of the application.

Both have their uses.

But in one area the BJT excels: C-E leakage current, which is practically negligible.
Not so with the MOSFET, where D-S leakage current is significant, especially at higher ambient temperature.

It's an engineering decision

[S. Petrukhin]

Like conventional transistors, they have their own characteristics. Their advantage is only in reducing the number of components, they are more convenient only. In the design, you need to study all their characteristics as a normal transistor. But you should pay attention that the resistors installed inside with ordinary digital signals introduce the transistor into deep saturation and this affects the speed characteristics.