Ultimate Transistor Selection Guide: How to Choose

Choosing the right transistor is the difference between a high-performance circuit and a pile of burnt silicon. At ElxHub, we categorize transistors into two main families: Bipolar Junction Transistors (BJT) for current-controlled tasks and Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFET) for high-efficiency voltage-controlled switching. This guide breaks down our library by application, power rating, and polarity to help you pick the perfect part.

Table of Contents show

The Master Transistor & MOSFET Comparison Table

Use this table to quickly find a transistor based on its maximum voltage (VCE or VDS) and current (IC or ID) handling capabilities.

Part Number	Type	Polarity	Max Voltage	Max Current	Package	Best Use Case
BC547	BJT	NPN	45V	100mA	TO-92	Small Signal / Pre-amp
2N3904	BJT	NPN	40V	200mA	TO-92	General Switching
2N2222	BJT	NPN	40V	800mA	TO-92	High Speed Switch / Relays
BC337	BJT	NPN	45V	800mA	TO-92	Output Driver
TIP41C	BJT	NPN	100V	6A	TO-220	Power Amplifier
TIP120	Darlington	NPN	60V	5A	TO-220	High-Gain Motor Driver
2N3055	BJT	NPN	60V	15A	TO-3	Linear Power Supplies
BC557	BJT	PNP	-45V	-100mA	TO-92	Small Signal (Complement)
2N3906	BJT	PNP	-40V	-200mA	TO-92	General Switching
BC327	BJT	PNP	-45V	-800mA	TO-92	Output Driver
TIP42C	BJT	PNP	-100V	-6A	TO-220	Power (Complement)
TIP127	Darlington	PNP	-60V	-5A	TO-220	High-Gain High-Side Switch

1. Small Signal & General Purpose BJTs

Best for switching small LEDs, amplifying sensor signals, or basic logic.

NPN Type: BC547, 2N3904, 2N2222, BC337
PNP Type: BC557, 2N3906, BC327

2. Power & Darlington BJTs

Best for driving heavy loads (motors, solenoids) where high current gain is required.

High-Current NPN: TIP41C, 2N3055
NPN Darlington: TIP120
High-Current PNP: TIP42C
PNP Darlington: TIP127

Selection Table: Quick Reference

Requirement	Recommended Component
5V Microcontroller Switching	2N2222 (BJT) or IRLZ44N (Logic MOSFET)
High Power Audio Output	2N3055 or TIP41C / TIP42C pair
Battery Powered Logic	2N7000 or BS170
Large DC Motor Control	IRFZ44N or TIP120