Diodes Incorporated ZTX657STZ

Overview

ZTX657STZ from Diodes Incorporated is an NPN silicon planar medium-power high-voltage transistor with V_CEO = 300 V, I_C = 0.5 A continuous, P_tot = 1 W at T_amb = 25°C, h_FE ≥ 40 at I_C = 10 mA, and f_T = 30 MHz - used in high-voltage switching and linear regulator stages in industrial power supplies.

For engineers reviewing the ZTX657STZ datasheet, ZTX657STZ pinout, ZTX657STZ application, or ZTX657STZ equivalent, key selection criteria include verified 300 V V_CEO rating, TO-92-compatible leadform, confirmed h_FE min of 40 at low-mid current, and validated safe operating area up to 100 ms pulse width under DC derating.

Technical Context

This device operates as a single NPN bipolar junction transistor optimized for medium-power, high-voltage switching and amplification where robust breakdown margins and stable gain at 10–100 mA are required. It features V_(BR)CBO = 300 V, V_(BR)CEO = 300 V, and V_(BR)EBO = 5 V, with guaranteed saturation performance (V_CE(sat) ≤ 0.5 V at I_C = 100 mA, I_B = 10 mA).

Thermal design is supported by a maximum junction temperature of +200°C and storage range down to –55°C. Its f_T = 30 MHz at I_C = 10 mA, V_CE = 20 V enables use in moderate-speed switching applications such as relay drivers and SMPS auxiliary circuits.

Key Specifications

Pinout & Package

Package: TO-92 (E-Line compatible), through-hole, 3-lead plastic package with standard C-B-E pin assignment.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ZTX653STZ and MPSA42, ZTX657STZ delivers tighter h_FE consistency at mid-current, higher safe operating area margin for pulsed loads, and guaranteed 1 W dissipation in TO-92 - making it preferred for new designs targeting 230 VAC auxiliary rails and relay interfaces.

Availability

ZTX657STZ is available at Aetrix Electronics and suitable for industrial power supply auxiliary rails, high-voltage relay drivers, linear voltage regulator pass elements, and discrete PWM signal amplifiers requiring stable component supply and long-term manufacturability.

Supply support for ZTX657STZ 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 manufacturer of discrete semiconductors and analog ICs, headquartered in Plano, Texas, with design centers across Asia and manufacturing in Taiwan and China.

ZTX657STZ belongs to the ZTX series of high-voltage bipolar transistors designed specifically for industrial power conversion, relay control, and linear regulation where reliability under high-voltage stress and thermal cycling is critical.

FAQ

Is ZTX657STZ RoHS compliant and halogen-free?

Yes, ZTX657STZ is RoHS compliant and halogen-free per Diodes Incorporated's product change notice PCN-2018-014. The TO-92 package uses matte tin-plated leads and meets JEDEC J-STD-020 moisture sensitivity level 1 (MSL-1) requirements for unlimited floor life at ≤30°C/60% RH.

What is the maximum allowable base-emitter reverse voltage?

The absolute maximum V_EBO is 5 V, tested at I_E = 100 µA with collector open. Exceeding this risks permanent degradation of the emitter-base junction; external clamping is recommended in inductive switching applications where flyback voltages may exceed 3 V.

Can ZTX657STZ be used in avalanche mode?

No - ZTX657STZ is not characterized or rated for controlled avalanche operation. Its safe operating area curve is defined only for forward-biased conditions. For energy-absorbing applications, use purpose-designed avalanche-rated transistors such as the FMMT618 or ZTX851.

How does thermal resistance θ_JA compare between ZTX657STZ and ZTX656STZ?

Both share identical TO-92 packaging and die construction, resulting in matched θ_JA ≈ 200°C/W on FR-4 with 1-inch² copper pad. No thermal performance difference exists between the two variants; selection should be based solely on required V_CEO rating (300 V vs. 200 V) and h_FE target at operating current.