2N5551 Amplifier PNP Transistor
The 2N5551 is an NPN bipolar junction transistor designed for high-voltage and low-to-medium current applications. It supports a collector-emitter voltage of 160 V and a collector current of 600 mA, making it ideal for audio amplification, analog signal stages, and general-purpose switching tasks.
You can drive it into conduction by applying a base-emitter voltage of ~0.7 V, allowing current to flow from collector to emitter. When you remove the base current, the transistor stops conducting, which makes it highly reliable for logic control and analog interfacing.
This transistor complements the PNP 2N5401, making the pair useful in push-pull amplifiers and symmetrical designs. Designers often pair the 2N5551 with its PNP complement, the 2N5401, to form push-pull amplifier stages, symmetric analog stages, or complementary switching pairs. This pairing enhances circuit efficiency and simplifies designs that require both sourcing and sinking current paths.
Pin Configuration (TO-92 Package)
| Pin | Name | Description |
|---|---|---|
| 1 | Emitter | Current flows out |
| 2 | Base | Controls switching or gain |
| 3 | Collector | Current flows in |
Key Features
Handles up to 160 V collector-emitter
Supports 600 mA collector current
Provides DC gain (hFE) of 100–300
Performs well in analog and low-frequency stages
Comes in a compact TO-92 plastic package
Switches moderately fast (~100 MHz fT)
Works as an NPN counterpart to 2N5401
Applications
Amplify signals in audio and analog circuits.
Switch high-voltage loads in control systems.
Build discrete transistor amplifiers.
Drive display panels, relays, and LEDs.
Design voltage-level shifting or interfacing stages.
Implement active filters or gain stages.
Use in preamp or postamp stages for audio.
Construct push-pull amplifier stages with 2N5401.
Use in power regulators and biasing networks.
Support education for high-voltage transistor behavior.
Specifications Table
| Parameter | Value |
|---|---|
| Transistor Type | NPN |
| Max Collector Current | 600 mA |
| Max Collector-Emitter Voltage | 160 V |
| Max Collector-Base Voltage | 180 V |
| Max Emitter-Base Voltage | 6 V |
| DC Current Gain (hFE) | 100–300 |
| Max Power Dissipation | 625 mW |
| Transition Frequency (fT) | ~100 MHz |
| Collector Saturation Voltage | ~0.3–0.75 V |
| Package Type | TO-92 ‘ |
| Operating Temperature | -55 to +150 °C |
