Diodes Incorporated ZTX601

Overview

ZTX601 from Zetex Semiconductors (now Diodes Incorporated) is an NPN silicon planar medium-power Darlington transistor designed for high-voltage switching and linear amplification in industrial control and power management circuits. It delivers 160 V_CEO, 1 A continuous collector current, DC current gain up to 100k at I_C = 50 mA, 1 W total power dissipation at 25°C ambient, and V_CE(sat) ≤ 1.2 V at I_C = 1 A / I_B = 10 mA - enabling efficient low-side switching in relay drivers and lamp ballasts.

For engineers reviewing the ZTX601 datasheet, ZTX601 pinout, ZTX601 application, or ZTX601 equivalent, key selection criteria include verified V_CEO = 160 V, guaranteed h_FE ≥ 5k at I_C = 1 A, thermal derating slope of 5.7 mW/°C above 25°C, and TO-92-compatible E-Line package with confirmed C-B-E terminal assignment.

Technical Context

The ZTX601 implements a monolithic Darlington pair structure with integrated base-emitter resistor network absent - requiring external base drive control. Its high h_FE (up to 100k) reduces required base current by ~100× versus single transistors, while V_CEO = 160 V and V_CBO = 180 V support operation in 120 V AC line-synchronized circuits.

It exhibits f_T = 150–250 MHz under I_C = 100 mA / V_CE = 10 V, but switching performance is limited by t_on = 0.75 µs and t_off = 2.2 µs at I_C = 0.5 A - indicating suitability for <100 kHz switching, not RF or high-speed digital applications.

Key Specifications

Pinout & Package

Package: TO-92-compatible E-Line (3-206), molded plastic, through-hole mounting. Dimensions and lead spacing match JEDEC TO-92 standards.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ZTX600 and BCX38, the ZTX601 uniquely balances 160 V blocking, Darlington-level gain, and TO-92 form factor - making it irreplaceable in 120 V relay drivers where both voltage margin and low base current are mandatory.

Availability

ZTX601 is available at Aetrix Electronics and suitable for industrial relay drivers, lamp ballast control, motor commutation, and power supply enable switching requiring stable component supply across extended production lifecycles.

Supply support for ZTX601 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

Zetex Semiconductors, acquired by Diodes Incorporated in 2008, specialized in high-performance discrete semiconductors for industrial, automotive, and power management applications.

The ZTX series was engineered specifically for robust medium-power linear and switching applications demanding high V_CEO, predictable h_FE, and reliable TO-92 packaging - targeting cost-sensitive yet thermally demanding industrial controls.

FAQ

Is ZTX601 pin-compatible with ZTX600?

Yes - both use identical E-Line TO-92 (3-206) package with confirmed C-B-E pinout. Mechanical and solder footprint compatibility is guaranteed. However, ZTX601 offers higher V_CEO (160 V vs. 140 V) and higher h_FE (up to 100k vs. 20k), so substitution is safe only if voltage stress remains within ZTX600's 140 V limit.

What is the maximum safe operating temperature for ZTX601 at 1 A collector current?

At I_C = 1 A and V_CE = 1.2 V, power dissipation is 1.2 W. With P_tot = 1 W at 25°C and derating of 5.7 mW/°C, junction temperature exceeds rating unless ambient is reduced to ≤10°C or heatsinking is added. For continuous 1 A operation, forced air or a 20°C/W heatsink is recommended.

Does ZTX601 include a built-in base-emitter resistor?

No - ZTX601 is a bare Darlington transistor with no integrated base biasing components. External base current must be supplied via a series resistor or active driver. This differs from "digital transistors" like MMBT2222A, which integrate R₁/R₂; ZTX601 requires explicit base current design per h_FE and load conditions.

Can ZTX601 be used in Class AB audio amplifier output stages?

No - its f_T (150–250 MHz) and h_FE variation with I_C make it unsuitable for linear audio amplification. Designed for switching and saturated-region operation, it lacks the consistent gain flatness, low distortion, and SOA stability required for audio output devices. Use complementary pairs like BD139/BD140 instead.