Diodes Incorporated ZTX601STZ

Overview

ZTX601STZ from Diodes Incorporated is an NPN silicon planar medium-power Darlington transistor with V_CEO = 160 V, I_C = 1 A continuous, h_FE ≥ 5 k at I_C = 1 A, P_tot = 1 W at T_amb = 25°C, and TO-92 compatible E-Line package - used in high-gain switching and linear amplification stages of industrial power supplies and relay drivers.

For engineers reviewing the ZTX601STZ datasheet, ZTX601STZ pinout, ZTX601STZ application, or ZTX601STZ equivalent, key selection criteria include verified Darlington gain at 1 A load, V_CEO derating behavior above 25°C, safe operating area (SOA) limits under pulsed conditions, and thermal resistance compatibility with PCB copper pour layouts.

Technical Context

This device implements a monolithic Darlington pair architecture with integrated base-emitter resistor network absent - requiring external base drive control. It delivers high DC current gain (h_FE up to 100 k in Group B) while maintaining V_CE(sat) ≤ 1.2 V at I_C = 1 A / I_B = 10 mA, enabling efficient low-side switching in 12–48 V systems.

Its f_T = 150–250 MHz and C_obo = 10–15 pF support moderate-speed switching (t_on/t_off = 0.75/2.2 µs), and the −55°C to +200°C junction temperature range supports operation in thermally demanding environments without forced cooling.

Key Specifications

Pinout & Package

Package: TO-92 (E-Line compatible, 3-206 outline), plastic encapsulated, through-hole mounting. Standard lead form with 0.1" pitch; leads pre-tinned for solderability.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ZTX600STZ, ZTX601STZ offers 20 V higher blocking voltage and ≥2.5× gain at 1 A - critical for reliable switching in 48 V industrial systems. Versus MJD122G, it trades thermal headroom for footprint reduction, making it optimal for compact, convection-cooled designs.

Availability

ZTX601STZ is available at Aetrix Electronics and suitable for industrial relay drivers, DC motor controllers, linear regulator pass elements, and overvoltage crowbar circuits requiring stable component supply across extended temperature ranges and multi-year production cycles.

Supply support for ZTX601STZ 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 China, Taiwan, and Malaysia.

ZTX601STZ belongs to the ZTX series of high-voltage, medium-power bipolar transistors engineered for ruggedized industrial switching and linear regulation - emphasizing reliability under thermal stress and long-term parametric stability.

FAQ

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

At T_amb = 70°C, derating begins at 0.0057 W/°C from the 1 W maximum. Power allowed = 1 − (70 − 25) × 0.0057 = 0.74 W. Using V_CE(sat) ≈ 1.0 V at I_C = 1 A, max I_C ≈ 0.74 A. This assumes minimal PCB copper; actual value depends on layout thermal resistance.

Does ZTX601STZ include a built-in base-emitter resistor?

No. ZTX601STZ is a bare Darlington transistor without integrated biasing resistors. External base current must be supplied via a series resistor or active driver. This allows precise control of saturation depth and switching speed but requires careful R_B selection to avoid overdrive or slow turn-on.

Can ZTX601STZ replace ZTX602 in existing designs?

ZTX602 has V_CEO = 180 V and higher h_FE (up to 20 k at 1 A). While ZTX601STZ shares the same TO-92 package and pinout, its 160 V rating and lower gain may cause marginal performance in 160–180 V applications or high-impedance base drive circuits. Verify V_CEO margin and h_FE under actual load before substitution.

Is the TO-92 package electrically insulated between collector and case?

Yes. The TO-92 plastic package used for ZTX601STZ provides full electrical isolation between the collector lead and the molded body. No thermal pad or metal tab is connected to the collector; thermal transfer occurs solely through lead conduction. This simplifies mounting on non-isolated PCBs without additional insulating hardware.