The S9013 is a very common NPN bipolar junction transistor (BJT) used in electronics for switching and amplification.
 
Basic Description
Type: NPN transistor
Package: TO-92 (through-hole)
Purpose: General-purpose signal amplification and switching
 
Key Specifications
Collector-Emitter Voltage (Vce): ~25–40V
Collector Current (Ic): up to 500mA
Power Dissipation: ≈625mW
Gain (hFE): ~60 to 300
Frequency (ft): ~150 MHz
 
Pin Configuration (TO-92)
When flat side faces you (legs down):
Collector
Base
Emitter
 
Common Uses
Switching LEDs, relays, motors
Amplifiers (audio or sensor signals)
Microcontroller interfacing (e.g., Arduino, NodeMCU)
 
Simple Example
If you use it with Arduino:
Apply small current to Base
It allows larger current from Collector → Emitter
Used to drive loads like relay or buzzer
 
Equivalent / Alternatives
You can replace S9013 with:
2N2222
BC337
2N3904
 
Important Tip
Always use a base resistor (e.g., 1kΩ) to protect your microcontroller.