Diodes Incorporated ZTX658STZ

Overview

ZTX658STZ 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, and f_T = 50 MHz - designed for telephone dialler circuits requiring robust voltage handling and reliable switching under pulsed loads.

For engineers reviewing the ZTX658STZ datasheet, ZTX658STZ pinout, ZTX658STZ application, or ZTX658STZ equivalent, key selection criteria include verified 400 V V_CEO rating, 100 mA–200 mA h_FE range at V_CE = 5 V, V_CE(sat) ≤ 0.5 V at I_C = 100 mA / I_B = 10 mA, thermal resistance R_th(j-amb) = 175 °C/W on PCB, and TO-92 compatible E-Line package footprint.

Technical Context

This discrete NPN bipolar junction transistor operates in linear or switching mode with guaranteed breakdown voltages of 400 V across both C–B and C–E terminals, enabling use in off-line telephony interface stages where transient overvoltage immunity is critical. Its f_T = 50 MHz and C_obo = 10 pF support moderate-speed switching up to ~100 kHz duty-cycled operation.

Thermal design relies on validated R_th(j-amb) = 175 °C/W (free air) and 116 °C/W (PCB-mounted), with safe operating area (SOA) defined for single-pulse conditions up to 100 V and 100 mA. Switching times are specified as 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.

Key Specifications

Pinout & Package

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

Key Features

Applications

Equivalent & Alternatives

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

Compared with ZTX658STZ, ZTX653STZ trades 100 V voltage margin for higher h_FE, while BCV61B sacrifices power handling and through-hole compatibility for miniaturization - neither offers full functional equivalence in legacy telephone hardware.

Availability

ZTX658STZ is available at Aetrix Electronics and suitable for telephone dialler circuits, off-line AC-DC interface stages, and industrial signal isolation drivers requiring stable component supply across long-lifecycle telecom and embedded equipment programs.

Supply support for ZTX658STZ 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 power management, signal integrity, and connectivity applications.

ZTX658STZ belongs to the ZTX series of high-voltage bipolar transistors engineered specifically for legacy and cost-sensitive telephony, industrial control, and pulse-generation applications demanding proven reliability and TO-92 compatibility.

FAQ

What is the maximum safe continuous collector current for ZTX658STZ at 70°C ambient?

At T_amb = 70°C, derating applies at 5.7 mW/°C above 25°C. With 45°C rise, power must be reduced by 256.5 mW, limiting P_tot to 743.5 mW. Using V_CE(sat) ≈ 0.35 V, max continuous I_C is approximately 2.1 A × (743.5 mW / 1 W) ≈ 450 mA - but absolute I_C rating remains 500 mA regardless of temperature.

Can ZTX658STZ be used in avalanche mode for energy clamping?

Yes - its 400 V V_CEO rating is tested under pulsed conditions with defined SOA limits. The device exhibits controlled avalanche behavior with specified I_CM = 1 A peak pulse current, making it suitable for passive clamping in telephone dialler transformer flyback protection without external TVS diodes.

Is the ZTX658STZ pinout identical to standard TO-92?

Yes - pinout is E-B-C (left-to-right, flat side facing, leads down), matching JEDEC TO-92 outline and compatible with ZTX650–ZTX659 series. This allows direct substitution in existing TO-92 footprints without board modification or adapter.

What is the typical h_FE at I_C = 10 mA and V_CE = 5 V?

Per datasheet Electrical Characteristics table, h_FE is specified as min 50, typ 100, max 400 at I_C = 10 mA and V_CE = 5 V. Typical value of 100 means expected DC current gain is sufficient for base resistor drive from 3.3 V or 5 V logic with ~100 kΩ–1 MΩ bias networks.