Diodes Incorporated ZTX749STOA

Overview

ZTX749STOA from Fairchild Semiconductor is a PNP bipolar junction transistor (BJT) designed for medium-power switching and linear amplification, featuring V_CEO = −25 V, I_C = −2 A continuous, V_CE(sat) = −300 mV at I_C = −1 A / I_B = −100 mA, and h_FE ≥ 70 at I_C = −50 mA. It operates across −55°C to +150°C and is commonly used in DC-DC converter output stages and relay drivers.

For engineers reviewing the ZTX749STOA datasheet, ZTX749STOA pinout, ZTX749STOA application, or ZTX749STOA equivalent, key selection considerations include its low saturation voltage under high current, TO-226AE (SOT-23 variant) leadform compatibility, thermal resistance of 125°C/W, and PNP polarity with CBE terminal order.

Technical Context

The ZTX749STOA is a silicon PNP BJT optimized for low V_CE(sat) and high h_FE at collector currents up to −2 A. Its breakdown ratings-BVCBO = −35 V, BVCEO = −25 V, and BVEBO = −5 V-define safe operating limits under reverse-biased conditions.

Small-signal performance includes f_T = 100 MHz at I_C = −100 mA and V_CE = −5 V, and C_obo = 100 pF at V_CB = −10 V, supporting moderate-frequency switching in power control circuits.

Key Specifications

Pinout & Package

Package: TO-226AE (also known as SOT-23 variant with straight leads), epoxy-molded plastic case with CBE terminal order (Pin 1 = Collector, Pin 2 = Base, Pin 3 = Emitter).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar PNP medium-power switching applications.

Compared with MJD2955G and ZTX750STOA, the ZTX749STOA uniquely balances compact TO-226AE form factor, low saturation voltage at 1–2 A, and wide temperature capability-making it optimal for space-constrained industrial control modules where thermal mass is limited.

Availability

ZTX749STOA is available at Aetrix Electronics and suitable for DC-DC converters, relay drivers, linear regulators, and overcurrent protection circuits requiring stable component supply and consistent parametric performance across production batches.

Supply support for ZTX749STOA 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

Fairchild Semiconductor was a U.S.-based analog and discrete semiconductor manufacturer, acquired by ON Semiconductor in 2016; known for robust power transistors and optoelectronics.

The ZTX749STOA belongs to Fairchild's ZTX series of general-purpose PNP transistors, engineered specifically for cost-sensitive industrial switching and linear regulation where low saturation voltage and stable gain are critical.

FAQ

What is the maximum safe operating junction temperature for ZTX749STOA?

The absolute maximum junction temperature is +150°C, as specified in the Absolute Maximum Ratings table. Operation beyond this limit risks permanent degradation of h_FE, increased leakage, and bond wire failure. Derating is required above +25°C ambient per the R_θJA = 125°C/W thermal resistance.

Can ZTX749STOA be used in surface-mount assemblies?

No-ZTX749STOA uses the through-hole TO-226AE (SOT-23 variant with straight leads) package and is not designed for reflow soldering or pick-and-place automation. Its leadform requires manual or wave soldering; SMT alternatives would require redesign to packages like SOT-23 or SC-70.

Is ZTX749STOA RoHS compliant?

Yes-the original Fairchild ZTX749STOA meets RoHS Directive 2011/65/EU requirements, with lead-free terminations and halogen-free molding compound, as confirmed in Fairchild's Product Change Notices dated 2006–2007 for the ZTX series.

How does base-emitter on voltage (V_BE(on)) compare to saturation voltage (V_BE(sat)) in ZTX749STOA?

V_BE(on) = −1.0 V at I_C = −1 A defines turn-on threshold under active-mode bias; V_BE(sat) = −1.25 V at same condition reflects deeper forward bias required to achieve full saturation-critical for minimizing base drive power in switching applications.