Overview
A 300-piece transistor assortment covering the four most-used small-signal bipolar transistors: S9012 (PNP), S9013 (NPN), S9014 (NPN, low-noise), and S8050 (NPN, higher-current). With 75 of each, this kit gives you a complete general-purpose transistor library for switching small loads, building amplifier stages, driving relays, level-shifting signals, audio pre-amps, and oscillator circuits. The selection is paired so you have both NPN (most-common) and PNP (high-side switching, complementary pairs) options on hand.
Each transistor is in a TO-92 plastic package with axial leads, the standard hobbyist form factor. They drop directly onto a breadboard, perfboard, or through PCB through-hole pads. The included plastic case has labelled compartments so each part type stays separated — critical because S8050 and S9013 look identical until you read the laser-etched part number on the flat side of the package.
Use this kit for everything from a 12V relay driver (S8050 NPN) to an audio pre-amp (S9014 low-noise NPN), a high-side LED switch (S9012 PNP), or a basic logic-inverter circuit. The four parts together cover essentially every small-signal transistor application you'll meet.
At a Glance
Per-Type Specifications
| Part | Type | VCEO | IC max | PD max | hFE | Best For |
| S9012 | PNP | -25V | -500 mA | 625 mW | 120-400 | High-side switching, complementary pair |
| S9013 | NPN | +25V | +500 mA | 625 mW | 120-400 | General-purpose switching, signal amp |
| S9014 | NPN | +45V | +100 mA | 450 mW | 200-1000 | Low-noise amplifier, audio pre-amp |
| S8050 | NPN | +25V | +1.5 A | 625 mW | 85-300 | Higher-current switching, relay drive |
Pinout (TO-92, Flat Side Facing You)
| Pin Position (left to right, flat facing you) | S9012, S9013, S9014, S8050 |
| Pin 1 (left) | Emitter (E) |
| Pin 2 (middle) | Base (B) |
| Pin 3 (right) | Collector (C) |
Common Circuit Examples
Driving a 12V Relay or Motor with S8050 (NPN)
Use the S8050 (1.5A capable) to switch a 12V load on/off from an Arduino digital pin. The transistor sits between the load's negative side and ground.
| Wire | Connection |
|---|---|
| Arduino Digital Pin (e.g., D2) | → 1 kΩ resistor → Base of S8050 |
| Emitter of S8050 | → GND |
| Collector of S8050 | → Negative side of load (relay coil, motor, etc.) |
| Positive side of load | → +12V |
| Across load (relay/motor) | 1N4148 or 1N4001 flyback diode, cathode to +12V |
Setting the digital pin HIGH turns the transistor ON, completing the circuit through the load. Setting LOW turns it OFF. The flyback diode protects against the inductive kick when the relay coil de-energises.
High-Side Load Switch with S9012 (PNP)
For loads where the negative side must be permanently grounded (LEDs, sensors that share a common ground), switch the positive supply with the PNP S9012. Note the inverted logic: HIGH on the input turns OFF the load.
| Wire | Connection |
|---|---|
| Emitter of S9012 | → +5V (or +Vcc) |
| Collector of S9012 | → Positive side of load |
| Base of S9012 | → 1 kΩ → Arduino digital pin |
| Negative side of load | → GND |
Pull the digital pin LOW to turn the load ON; HIGH to turn off.
Single-Stage Audio Pre-Amp with S9014
The S9014 has high beta (gain) and low noise — a typical pick for a microphone or guitar pre-amp. Bias the transistor with two resistors and AC-couple the input/output with electrolytic capacitors.
| Component | Value | Purpose |
|---|---|---|
| RB1 (Vcc → Base) | 100 kΩ | Top of base voltage divider |
| RB2 (Base → GND) | 22 kΩ | Bottom of divider; sets bias point |
| RC (Vcc → Collector) | 4.7 kΩ | Collector load resistor |
| RE (Emitter → GND) | 1 kΩ | Emitter degeneration / stability |
| Cin, Cout | 1 µF electrolytic | AC coupling, blocks DC bias |
Output is at the collector (Vcc = 5V or 9V). Voltage gain ~ RC / RE = 4.7 (about 13 dB).