onsemi BC557ZL1

Overview

BC557ZL1 from onsemi is a PNP silicon small-signal amplifier transistor in TO-92 package, rated for V_CEO = –45 V, I_C = –100 mA continuous, and h_FE = 120–800 (depending on grade), commonly used in low-power linear amplification and switching stages of audio preamps, sensor interfaces, and discrete logic level translation circuits.

For engineers reviewing the BC557ZL1 datasheet, pinout, applications, or equivalent options, this page delivers verified electrical parameters, thermal behavior, package dimensions, real-world use cases, and validated alternative transistors - all specific to the BC557ZL1 variant with Ammo Pack packaging and B-grade h_FE binning.

Technical Context

The BC557ZL1 operates as a general-purpose PNP bipolar junction transistor optimized for linear amplification and saturated switching in ambient-temperature-stable circuits. Its DC current gain spans 120–800 across A/B/C variants, with typical f_T = 320 MHz at I_C = –10 mA and V_CE = –5 V, and V_BE(sat) ≤ –0.7 V at I_C = –100 mA / I_B = –5 mA.

Thermal design is constrained by R_θJA = 200°C/W (free-air) and R_θJC = 83.3°C/W, supporting operation from –55°C to +150°C junction temperature. Its Cob = 3.0–6.0 pF at V_CB = –10 V enables stable high-frequency biasing in RF-adjacent analog stages.

Key Specifications

Pinout & Package

BC557ZL1 uses the standard TO-92 (Case 29, Style 17) plastic package with 3 leads, designed for through-hole mounting and manual prototyping. Dimensions comply with ANSI Y14.5M-1982; lead pitch is 2.54 mm, body height ~4.7 mm, and maximum dissipation is 625 mW at T_A = 25°C.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar PNP small-signal amplifier applications.

Compared with BC557BRL1 (same device, different packaging), BC557ZL1 offers identical electrical performance in Ammo Pack format for manual or semi-automated assembly; versus BC807-25, BC557ZL1 provides proven through-hole reliability and easier prototyping but lacks SMT scalability.

Availability

BC557ZL1 is available at Aetrix Electronics and suitable for audio preamplifiers, sensor signal conditioners, and discrete logic level shifters requiring stable component supply across industrial, instrumentation, and educational electronics programs.

Supply support for BC557ZL1 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

onsemi (formerly ON Semiconductor) is a global semiconductor supplier specializing in energy-efficient power management, analog, and sensing solutions for automotive, industrial, and cloud infrastructure markets.

The BC557 series belongs to onsemi's legacy general-purpose bipolar transistor family, engineered for cost-sensitive, high-reliability linear and switching applications where consistent h_FE, low noise, and wide temperature operation are essential.

FAQ

What is the exact h_FE range specified for BC557ZL1?

The BC557ZL1 is a B-grade variant of the BC557 family, with h_FE guaranteed between 120 and 270 when tested at I_C = –2.0 mA and V_CE = –5.0 V. This binning is confirmed in the official onsemi BC556/D datasheet Rev. 1, page 3, under "DC Current Gain" for B Series Devices. The ZL1 suffix denotes Ammo Pack packaging but does not alter the electrical grading.

Is BC557ZL1 pin-compatible with BC547 or BC558?

No - BC557ZL1 is not pin-compatible with BC547 (NPN) due to opposite polarity and different internal structure. While BC557ZL1 and BC558 share the same TO-92 pinout (Collector-Base-Emitter), they differ in V_CEO (–45 V vs. –30 V) and safe operating area, so substitution requires verification of voltage margin in the target circuit. BC557ZL1 pinout is fixed per Style 17: Pin 1 = Collector, Pin 2 = Base, Pin 3 = Emitter.

What is the maximum power dissipation for BC557ZL1 at 75°C ambient?

At T_A = 75°C, BC557ZL1's maximum power dissipation is derated from 625 mW using the 5.0 mW/°C factor: 625 mW − (5.0 mW/°C × (75 − 25)°C) = 375 mW. This assumes free-air mounting (R_θJA = 200°C/W); actual dissipation may be higher with heatsinking or PCB copper area, but the device's R_θJC = 83.3°C/W limits case-to-junction thermal rise.

Does BC557ZL1 support operation at 125°C junction temperature?

Yes - BC557ZL1 is rated for T_J = –55°C to +150°C, and its Safe Operating Area (SOA) curves (Figure 14, page 6) explicitly include single-pulse operation up to 150°C. At T_J = 125°C, h_FE decreases by ~0.5%/°C from 25°C values, and V_BE(on) shifts negatively by ~2.2 mV/°C, both documented in Figures 4 and 8 of the datasheet.

Can BC557ZL1 be used in Class-A audio amplifier output stages?

BC557ZL1 is suitable for low-power Class-A preamp or driver stages (e.g., <10 mW output), but not for final output stages due to its 625 mW P_D limit and lack of complementary NPN pairing in the same package. For symmetric push-pull output, it must be paired with an NPN like BC547B; however, thermal mismatch and h_FE asymmetry require careful biasing. Its 320 MHz f_T and 2.0 dB NF make it ideal for voltage gain, not power delivery.