onsemi BC618

Overview

BC618 from ON Semiconductor is an NPN silicon Darlington transistor in TO-92 package, rated for 55 V_CEO, 1.0 A continuous collector current, and 625 mW power dissipation at 25°C ambient. It delivers high DC current gain (h_FE = 2000–10000 at I_C = 10–200 mA), low V_CE(sat) ≤ 1.1 V, and f_T = 150 MHz, enabling use in high-gain switching and linear amplification stages of industrial control interfaces.

For engineers reviewing the BC618 datasheet, pinout, applications, or equivalent options, key selection criteria include its Darlington architecture for high-current drive with minimal base drive, thermal resistance (R_JA = 200°C/W), Pb-free TO-92 packaging, and verified noise performance (e_n < 2 nV/√Hz at 1 kHz) in low-level analog signal paths.

Technical Context

The BC618 integrates two cascaded NPN transistors in a monolithic Darlington configuration, delivering ultra-high current gain without external bias networks. Its V_BE(sat) ≤ 1.6 V and V_CE(sat) ≤ 1.1 V at I_C/I_B = 1000 ensure efficient saturation in relay drivers and lamp controllers.

Designed for operation across −55°C to +150°C junction temperature, it supports stable gain (h_FE variation < ±20% over temperature) and exhibits low output capacitance (C_ob = 4.5–7.0 pF) and input capacitance (C_ib = 5.0–9.0 pF), enabling reliable performance in audio preamplifier and sensor interface circuits.

Key Specifications

Pinout & Package

BC618 is housed in a standard TO-92 (Case 29, Style 17) plastic package with 3 leads, lead-free compliant per J-STD-020, and marked "BC618" with date code (AYWW format). The package provides mechanical robustness for through-hole assembly and meets IPC-J-STD-002 solderability requirements.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar Darlington transistor applications.

Compared with BC619 and MPSA13, the BC618 uniquely balances 55 V ruggedness, 2000+ h_FE, and sub-1.2 V saturation in a cost-effective TO-92 package-making it optimal for 24 V industrial controls where both gain and voltage margin are tightly constrained.

Availability

BC618 is available at Aetrix Electronics and suitable for industrial relay drivers, audio preamplifier stages, thermal sensor interfaces, LED current regulators, and low-noise analog front-ends requiring stable component supply and long-term manufacturability.

Supply support for BC618 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

ON Semiconductor (now onsemi) is a global semiconductor supplier specializing in energy-efficient power, analog, sensor, and connectivity solutions for automotive, industrial, cloud, and consumer markets.

The BC618 belongs to onsemi's legacy bipolar transistor product line, designed specifically for high-gain, medium-power linear and switching applications in industrial automation, instrumentation, and audio systems.

FAQ

What is the maximum continuous collector current rating for BC618?

The BC618 is rated for 1.0 A continuous collector current (I_C) at T_A = 25°C. Derating is required above 25°C ambient: 5.0 mW/°C for the 625 mW rating or 12 mW/°C for the 1.5 W rating when mounted on a PCB with sufficient copper area. Actual usable current depends on thermal design and PCB layout.

Does BC618 have Pb-free packaging options?

Yes, BC618RL1G and BC618G are Pb-free versions of the BC618, fully compliant with RoHS Directive 2011/65/EU. These variants use matte tin lead finish and meet J-STD-020 moisture sensitivity level 1 (MSL-1), supporting standard reflow profiles without special baking requirements.

What is the typical DC current gain (hFE) of BC618 at 100 mA collector current?

At I_C = 100 mA and V_CE = 5.0 V, the BC618 exhibits h_FE = 4000 (typical) and up to 10000 (max), per the official ON Semiconductor datasheet. This high gain remains stable across −55°C to +125°C, making BC618 suitable for temperature-critical industrial applications.

Can BC618 be used in linear amplifier configurations?

Yes, BC618 supports linear operation with verified small-signal parameters: f_T = 150 MHz, |h_fe| > 100 at 100 MHz, and low noise voltage (<2 nV/√Hz). Its Darlington structure provides high input impedance and gain stability, enabling use in audio preamps and sensor signal conditioning where distortion and noise are critical.

What is the pin configuration for BC618 in TO-92 package?

When viewing the flat side of the BC618 TO-92 package with leads pointing downward, the pinout is: Pin 1 = Collector, Pin 2 = Base, Pin 3 = Emitter. This matches Case 29, Style 17 mechanical drawing and is confirmed in the ON Semiconductor BC618/D datasheet Figure 1 and Package Dimensions section.