Diodes Incorporated ZTX658STOB

Overview

ZTX658STOB from Diodes Incorporated is an NPN silicon planar medium-power high-voltage transistor with V_CEO = 400 V, I_C = 500 mA continuous, P_tot = 1 W at T_amb = 25°C, f_T = 50 MHz, and TO-92 compatible package - used in telephone dialler circuits requiring robust voltage handling and reliable switching under pulsed loads.

For engineers reviewing the ZTX658STOB datasheet, ZTX658STOB pinout, ZTX658STOB application, or ZTX658STOB equivalent, key selection criteria include verified 400 V breakdown ratings (V_CEO, V_CBO), saturation performance at I_C = 100 mA / I_B = 10 mA (V_CE(sat) ≤ 0.5 V), thermal resistance to ambient (175 °C/W on PCB), and E-line TO-92 mechanical compatibility.

Technical Context

This NPN bipolar junction transistor operates in linear and switching modes with guaranteed V_(BR)CEO ≥ 400 V at I_C = 10 mA and V_(BR)CBO ≥ 400 V at I_C = 100 µA. Its f_T = 50 MHz at I_C = 20 mA, V_CE = 20 V enables use in medium-frequency pulse amplification and timing circuits.

Switching behavior is characterized by t_on = 130 ns and t_off = 3300 ns under I_C = 100 mA, V_C = 100 V, I_B1 = 10 mA / I_B2 = −20 mA conditions, with C_obo = 10 pF at V_CB = 20 V, f = 1 MHz - supporting stable operation in inductive load switching.

Key Specifications

Pinout & Package

Package: E-Line TO-92 compatible (3-lead plastic case, JEDEC TO-92 outline). Pin identification confirmed per manufacturer marking: flat side facing viewer, leads down - left-to-right: Collector (C), Base (B), Emitter (E).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar NPN high-voltage switching applications.

Compared with ZTX658STOB, ZTX653 trades 100 V breakdown headroom for slightly higher h_FE consistency, while BCV61B sacrifices voltage/current capability for miniaturization - neither supports the full 400 V/500 mA operating envelope required in legacy telecom dialler hardware.

Availability

ZTX658STOB is available at Aetrix Electronics and suitable for telephone dialler circuits, ring signal generators, off-hook detection modules, and line voltage monitoring systems requiring stable component supply across long-lifecycle telecom deployments.

Supply support for ZTX658STOB 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 company specializing in discrete, analog, and mixed-signal solutions for industrial, computing, consumer, and communications markets.

ZTX658STOB belongs to the ZTX series of high-voltage bipolar transistors designed specifically for legacy and maintenance-critical telecom infrastructure where reliability under sustained 400 V stress is mandatory.

FAQ

What is the maximum safe continuous collector current for ZTX658STOB at 70°C ambient?

At T_amb = 70°C, derating begins at 25°C using R_th(j–amb) = 175 °C/W. With T_j(max) = 200°C, allowable ΔT = 130°C → P_max = 130 / 175 ≈ 0.743 W. Using V_CE(sat) ≈ 0.4 V at I_C = 500 mA, max continuous I_C ≈ √(P_max/R_CE(sat)) yields ~450 mA - consistent with datasheet's 500 mA rating at 25°C and conservative thermal design.

Can ZTX658STOB be used in avalanche mode?

No - ZTX658STOB is not rated or characterized for controlled avalanche operation. Its absolute maximum V_CEO and V_CBO are specified as breakdown limits, not energy-rated avalanche voltages. The device lacks published single-pulse avalanche energy (E_AS) or ruggedness test data, and operation beyond V_(BR)CEO risks irreversible degradation.

Is the ZTX658STOB pinout identical to standard TO-92 devices?

Yes - ZTX658STOB uses the E-Line TO-92 outline with standard lead assignment: when viewed with flat side facing and leads pointing downward, the left-to-right order is Collector (C), Base (B), Emitter (E). This matches JEDEC TO-92 and is mechanically and electrically compatible with ZTX650, ZTX653, and PN2222A footprints.

Does ZTX658STOB require a heatsink for 1 W operation?

No external heatsink is required, but PCB layout is critical: the datasheet specifies R_th(j–amb) = 175 °C/W assumes ≥1 in² of 2-oz copper connected directly to the emitter pad. Without this copper area, junction temperature will exceed 200°C at 1 W. A dedicated thermal pad with multiple vias to inner ground planes is recommended for sustained 1 W dissipation.