2SC1815 — NPN General Purpose Bipolar Junction Transistor

Overview

The 2SC1815 (often stamped simply as C1815) is a legendary general-purpose NPN bipolar junction transistor (BJT) manufactured originally by Toshiba and widely produced across the electronics industry. Enclosed in a standard TO-92 package, it is one of the most famous small-signal transistors in Japanese and Asian consumer electronics history.

Designed for low-noise audio frequency amplification, signal switching, relay drivers, and oscillator circuits, the 2SC1815 handles collector-emitter voltages up to $50\text{ Volts}$ and continuous collector currents up to $150\text{ mA}$ . It is commonly paired with its PNP complementary counterpart, the 2SA1015.

Quick reference


Transistor Type	NPN Bipolar Junction Transistor (BJT)
Package	TO-92 (Flat face front, leads pointing down)
Collector-Emitter Voltage ( $V_{CEO}$ )	$50\text{ V}$ max
Collector-Base Voltage ( $V_{CBO}$ )	$60\text{ V}$ max
Emitter-Base Voltage ( $V_{EBO}$ )	$5.0\text{ V}$ max
Continuous Collector Current ( $I_C$ )	$150\text{ mA}$ continuous ( $500\text{ mA}$ pulsed)
DC Current Gain ( $h_{FE}$ )	70 to 700 (Ranks: O: 70–140, Y: 120–240, GR: 200–400, BL: 350–700)
Transition Frequency ( $f_T$ )	$80\text{ MHz}$ min ( $250\text{ MHz}$ typical)

Pinout (TO-92 Package)

Looking at the flat face of the TO-92 package with leads pointing down:

text

        ┌─────────────┐
        │   C1815     │  (Flat Package Face)
        └─┬───┬───┬───┘
          1   2   3
          E   C   B

Pin	Name	Description
1	`EMITTER` (`E`)	Emitter terminal (Ground reference 0 V)
2	`COLLECTOR` (`C`)	Collector terminal (Load connection)
3	`BASE` (`B`)	Base terminal (Control input via current-limiting resistor)

Warning

Pinout Warning: 2SC1815 vs 2N3904 / BC547 Pinouts!

2SC1815 (TO-92): Pin 1 = Emitter, Pin 2 = Collector, Pin 3 = Base (E-C-B).
2N3904 (TO-92): Pin 1 = Emitter, Pin 2 = Base, Pin 3 = Collector (E-B-C).
BC547 (TO-92): Pin 1 = Collector, Pin 2 = Base, Pin 3 = Emitter (C-B-E).
Substituting a 2SC1815 for a 2N3904 or BC547 without checking the pinout will result in wrong lead connections!

Specifications

Parameter	Symbol	Min	Typ	Max	Unit	Conditions
Collector-Emitter Voltage	$V_{CEO}$	50	—	—	V	$I_C = 1\text{mA}, I_B = 0$
Collector Cutoff Current	$I_{CBO}$	—	—	100	nA	$V_{CB} = 60\text{V}, I_E = 0$
DC Current Gain	$h_{FE}$	70	—	700	—	$V_{CE} = 6\text{V}, I_C = 2\text{mA}$
Collector Saturation Volts	$V_{CE(sat)}$	—	0.1	0.25	V	$I_C = 100\text{mA}, I_B = 10\text{mA}$
Base Saturation Voltage	$V_{BE(sat)}$	—	—	1.0	V	$I_C = 100\text{mA}, I_B = 10\text{mA}$
Power Dissipation	$P_C$	—	—	400	mW	$T_A = 25^\circ\text{C}$

Common mistakes

Assuming E-B-C pinout: Japanese 2S-series TO-92 BJTs (like 2SC1815 and 2SA1015) use E-C-B pin layout (Pin 1 Emitter, Pin 2 Collector, Pin 3 Base). Beginners swapping 2SC1815 with Western 2N3904 (E-B-C) or European BC547 (C-B-E) often miswire the Base and Collector.
Omitting Base resistor ( $R_B$ ): BJTs are current-driven devices. Connecting an MCU GPIO pin directly to the Base destroys the base-emitter junction ( $V_{BE} \approx 0.7\text{V}$ ). Always include a series Base resistor (e.g. $1\text{ k}\Omega$ to $10\text{ k}\Omega$ ).

Notes

2SC1815 vs 2SA1015: 2SC1815 is NPN; 2SA1015 is its complementary PNP counterpart used in push-pull audio stages.