onsemi BC557AZL1G

Overview

BC557AZL1G 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, h_FE = 120–270 at I_C = −2 mA, f_T = 320 MHz, and V_CE(sat) = −0.3 V at I_C/I_B = 10 - used in low-power linear amplification and switching circuits in industrial control interfaces and sensor signal conditioning stages.

For engineers reviewing the BC557AZL1G datasheet, pinout, applications, or equivalent options, this page delivers verified electrical ratings, thermal limits, DC gain bands, saturation behavior, and real-world substitution guidance - all specific to the BC557A variant in Pb-free TO-92 packaging with ammo box delivery.

Technical Context

The BC557AZL1G operates as a general-purpose PNP bipolar junction transistor optimized for linear amplification and active-mode switching. Its h_FE range (120–270 @ I_C = −2 mA) supports stable biasing across temperature, while f_T = 320 MHz enables audio-frequency and low-MHz signal amplification. V_BE(on) = −0.62 to −0.7 V and V_CE(sat) = −0.3 V ensure predictable turn-on and low-loss saturation in emitter-follower and switch configurations.

Thermal design is constrained by R_JA = 200 °C/W (ambient) and R_JC = 83.3 °C/W (case), with safe operating area limited by second breakdown at high V_CE/I_C combinations. ICES ≤ −2.0 nA at V_CES = −20 V confirms low leakage in standby states, supporting reliable operation in battery-powered sensor nodes.

Key Specifications

Pinout & Package

BC557AZL1G uses the TO-92 (Case 29-11, Style 17) package with bent leads and Pb-free finish. Dimensions: 4.45–5.20 mm (L) × 4.32–5.33 mm (W) × 3.18–4.19 mm (H). Seating plane defined per ASME Y14.5M-1994.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BC557BZL1G and BC857B,215, the BC557AZL1G offers the lowest-cost through-hole solution with verified 320 MHz bandwidth and 2.0 dB noise performance - ideal for manual assembly, field service, and applications where thermal mass from TO-92 aids reliability under intermittent load.

Availability

BC557AZL1G is available at Aetrix Electronics and suitable for industrial sensor interfaces, audio preamplification stages, and discrete logic translation circuits requiring stable component supply, long-term obsolescence management, and RoHS-compliant sourcing.

Supply support for BC557AZL1G 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, sensing, and connectivity solutions for automotive, industrial, and cloud infrastructure markets.

The BC557AZL1G belongs to the BC556/557/558 family of general-purpose PNP transistors designed for cost-effective, reliable amplification and switching in consumer, industrial, and communication equipment where TO-92 form factor and Pb-free compliance are essential.

FAQ

What is the maximum collector-emitter voltage rating for BC557AZL1G?

The BC557AZL1G has a guaranteed V_CEO rating of −45 Vdc, meaning it can safely block up to 45 V between collector and emitter with base open. This rating applies across the full operating temperature range (−55°C to +150°C) and is validated per onsemi's stress testing protocol. Exceeding −45 V risks avalanche breakdown and permanent device failure. Always include ≥20% derating margin in BC557AZL1G circuit designs.

Does BC557AZL1G support lead-free soldering processes?

Yes, BC557AZL1G is explicitly marked as Pb-free in its ordering code ('ZL1G' suffix) and qualified for lead-free reflow soldering per J-STD-020. Its TO-92 package withstands peak temperatures up to 260°C for 30 seconds. The device meets RoHS Directive 2011/65/EU and is compatible with standard no-clean flux profiles. No special prebake or moisture sensitivity handling is required for BC557AZL1G.

What is the typical DC current gain (h_FE) range for BC557AZL1G at I_C = −2 mA?

Per the official onsemi datasheet, BC557AZL1G exhibits h_FE = 120–270 when tested at I_C = −2.0 mAdc and V_CE = −5.0 Vdc at 25°C. This range reflects production lot variation and must be accounted for in bias network design. For worst-case analysis, use h_FE(min) = 120 to ensure sufficient base drive; for power optimization, h_FE(max) = 270 informs minimum base resistor values in BC557AZL1G applications.

Can BC557AZL1G be used in high-frequency amplifier designs?

Yes, BC557AZL1G has a specified f_T of 320 MHz, enabling effective small-signal amplification up to approximately 100 MHz with usable gain. Its Cob = 3.0–6.0 pF and h_fe = 260–500 at 1 kHz support stable broadband response when properly decoupled and matched. However, BC557AZL1G is not characterized for RF power amplification or microwave frequencies; use dedicated RF transistors above 200 MHz.

How does BC557AZL1G differ from BC557BZL1G in practical circuit design?

The primary difference lies in DC current gain: BC557AZL1G has h_FE = 120–270, while BC557BZL1G specifies 180–420 at I_C = −2 mA. This means BC557BZL1G delivers higher gain with less base drive current, allowing smaller base resistors and lower quiescent power. Both share identical V_CEO, f_T, package, and thermal specs - so BC557AZL1G remains fully interchangeable where gain margin is acceptable, but BC557BZL1G improves efficiency in high-impedance bias networks.