I would like make a lot of small projects using ATmega328P (and other ATmega family) based Arduinos (UNO R3, old Nano and similar). That means USB power (5V, 0.5A max, but typically way less, like 100mA) and frequencies up to 16MHz. I want to use lot of BJT transistors for LED switching, sniffing …

[image] gilhad: What transistors I should buy? Any one that fits your needs. But why BJT and not MOSFET? My needs were <= 0.03$ and 15V, 100mA, 100mW at least. Best available in dual case (SMD and PTH) and handy pinout (E-B-C)..

Good question :slight_smile: Basically I had seen mainly BJT schemas around me, I started play with BJT 40 years ago (and no MOSFET was aviable for me at the time) and I remember when I got some informations about MOSFETs, it said they are expensive, hard to obtain, need big voltage and are easy de…

Hi Last year I bit the bullet and purchased a pack of assorted BJT from Ali. I tested a select few and they appear ok. I made the top label and the data label on the inside of the lid. Great for just opening and going ummm.. yes... no... that will do... when the protoboard is on the bench. […

I actually only have BC547 & BC557 as general purpose transistors in my box.

2N3904 and 2N3906 are my stock general purpose devices for controlling low power relays etc. Readily available in the UK.

[image] gilhad: 0-0.8V would be considered no signal and 2.5V-5V would be considered full signal I think you should first learn how a BJT works. They are current controlled current devices not voltage controlled. Maybe you are thinking about MOSFETs and not BJTs

Yes, you are right. I do somehow know it, but not actively. LEDs are also current controlled, but there is some threshold, where they do not operate (I mean shine) under - something like 2V for red, 2.5V for many other and 3V for blue (approx. ), so I can use (with some resistor) 2 red LEDs in ser…

[image] gilhad: I started play with BJT 40 years ago I started with electronic tubes 60 years ago :slight_smile: BJT are fine for analogue circuits while MOSFET are better suited for binary (ON/OFF, PWM...) output. MOSFETs should be logic level compatible (IRL...) and support the output volt…

[image] gilhad: And none of LEDs would shine for even highest values of LOW signal (Vol <= 1V) and every LED can be turned on even with lowest HIGH signal (Voh >=4.1V). Your pin voltage is not really relevant since you want to use transistor to drive the LEDs. Pick some BC337/BC327 from AE a…

[image] gilhad: MOSFETs within such range will be better for my needs For the needs described, forget about MOSFETs — regular BJT transistors already listed are perfectly fine. Consider MOSFETs only when driving high currents and when you can control the gate with voltages above 5 V (logic-le…

Universal PNP (and PNP) transistors (BJT) for ATmega328 based Arduinos - what to buy?

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LarryD October 14, 2025, 9:18pm 23

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Universal PNP (and PNP) transistors (BJT) for ATmega328 based Arduinos - what to buy?

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