Diodes Incorporated ZTX325STOB

Overview

ZTX325STOB from Diodes Incorporated is an NPN silicon planar RF transistor optimized for VHF/UHF amplification, featuring f_T = 1.3 GHz, noise figure < 5 dB at 500 MHz, and 175 mW output power at 500 MHz under 13.5 V_CE/22.5 mA bias. It operates with V_CEO = 15 V, V_CBO = 30 V, and P_tot = 350 mW in a TO-92 compatible package, commonly deployed in FM receiver front-ends and low-power RF driver stages.

For engineers reviewing the ZTX325STOB datasheet, ZTX325STOB pinout, ZTX325STOB application, or ZTX325STOB equivalent, key selection criteria include verified 500 MHz noise performance (N = 5.0 dB), transition frequency scalability across 2–25 mA collector current, output power linearity at V_CE = 13.5 V, and thermal stability up to +200°C junction temperature.

Technical Context

This device employs a planar epitaxial structure with optimized base-emitter junction geometry to achieve high f_T and low feedback capacitance (C_re = 0.85 pF). Its low r_bb'C_b'c time constant (2–12 ps) supports stable gain up to 1 GHz while maintaining low intermodulation distortion (–53 dB).

Designed for Class-A small-signal amplification, it delivers consistent h_FE = 25–150 across I_C = 2–25 mA at V_CE = 1 V, with C_TC = 1.5 pF and C_TE = 2.0 pF enabling predictable impedance matching at 500 MHz using standard 50 Ω source termination.

Key Specifications

Pinout & Package

Supplied in a TO-92 compatible through-hole package (E-Line 3-161 footprint), with leads identified as Emitter (E), Base (B), and Collector (C) - pin 1 = E, pin 2 = B, pin 3 = C when viewing flat side with leads down and left-to-right orientation.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MPSH10 and BFR92A, ZTX325STOB uniquely balances 500 MHz noise performance, 175 mW output capability, and TO-92 manufacturability-making it optimal for cost-sensitive, medium-power RF amplifiers where thermal margin and 500 MHz linearity are critical.

Availability

ZTX325STOB is available at Aetrix Electronics and suitable for FM receiver front-ends, UHF wireless microphone preamplifiers, and ISM-band sensor transmitters requiring stable component supply and proven RF performance at 500 MHz.

Supply support for ZTX325STOB 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

Diodes Incorporated is a global semiconductor manufacturer specializing in discrete devices, analog ICs, and timing solutions, with design centers in Asia, Europe, and North America.

ZTX325STOB belongs to Diodes' legacy RF transistor product line, engineered specifically for cost-effective, high-yield assembly in consumer and industrial RF amplifiers operating up to 1 GHz.

FAQ

What is the maximum safe operating collector current for continuous DC bias?

The mean collector current averaged over 100 µs is rated at 25 mA, and the peak collector current is 50 mA. For continuous DC operation, sustained current must not exceed 25 mA at T_amb ≤ 25°C, with linear derating to zero at 150°C case temperature per the thermal resistance curve in the official datasheet.

Can ZTX325STOB be used in common-base configuration for broadband amplification?

Yes - its low r_bb'C_b'c time constant (2–12 ps) and symmetrical C_TC/C_TE values (1.5 pF / 2.0 pF) make it well-suited for common-base operation up to 800 MHz, especially where input/output isolation and wideband gain stability are required.

Is the TO-92 package lead-form compatible with automated through-hole insertion equipment?

Yes - the ZTX325STOB uses the standard E-Line TO-92 footprint (3-161), with 0.4-inch lead spacing and straight lead form conforming to IPC-7351 Class B standards, enabling compatibility with standard wave solder and selective soldering fixtures.

Does the 175 mW output power specification require external matching components?

Yes - the 175 mW output power is measured under specific 500 MHz test conditions (V_CE = 13.5 V, I_C = 22.5 mA, P_in = 25 mW) using a defined input/output matching network. Achieving this performance in-circuit requires replicating those network impedances via discrete LC elements or microstrip stubs.