Diodes Incorporated ZTX601STOB

Overview

ZTX601STOB 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 ZTX601STOB datasheet, ZTX601STOB pinout, ZTX601STOB application, or ZTX601STOB equivalent, key selection criteria include verified Darlington gain linearity at 1 A, V_CE(sat) ≤ 1.2 V under I_C/I_B = 100, thermal derating slope of 5.7 mW/°C, and safe operating area compliance up to 160 V with pulsed I_CM = 4 A.

Technical Context

This Darlington pair integrates two NPN transistors monolithically to deliver high DC current gain (h_FE up to 100 k in Group B) while maintaining low base drive requirements - enabling direct microcontroller GPIO interfacing without external pre-driver stages. Its V_BE(sat) = 1.7–1.9 V at I_C = 1 A reflects dual-base-emitter junction conduction.

The device operates across –55°C to +200°C junction temperature range and supports pulsed switching with t_on = 0.75 µs and t_off = 2.2 µs at I_C = 0.5 A, V_CE = 10 V - suitable for medium-speed discrete power control where SOA-limited voltage/current trade-offs are managed via external source resistance (R_S).

Key Specifications

Pinout & Package

Supplied in E-Line TO-92 compatible package (3-206 outline), with molded plastic case, axial leads, and standard C-B-E terminal assignment.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ZTX600STOB, ZTX601STOB provides 20 V higher blocking voltage and 5× higher guaranteed gain - critical for noise-immune 1 A switching. Against MJD127G, it trades package size and power for TO-92 fit and superior voltage headroom in space-constrained 160 V designs.

Availability

ZTX601STOB is available at Aetrix Electronics and suitable for industrial relay drivers, DC motor start circuits, linear voltage regulator pass elements, and high-voltage sensor interface amplifiers requiring stable component supply across extended temperature ranges.

Supply support for ZTX601STOB 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, specializing in high-reliability components for industrial, automotive, and computing markets.

The ZTX series targets medium-power discrete switching and amplification, emphasizing ruggedness, wide temperature operation, and pin-compatible legacy upgrades for industrial control systems.

FAQ

What is the maximum safe collector-emitter voltage for ZTX601STOB in continuous DC operation?

The absolute maximum V_CEO is 160 V under open-base conditions at T_j ≤ 200°C. For reliable long-term operation, design margins should limit steady-state V_CE to ≤120 V, especially above 70°C ambient, to maintain SOA compliance and avoid second breakdown.

Can ZTX601STOB be driven directly from a 3.3 V microcontroller GPIO?

Yes - with appropriate base resistor calculation. At I_C = 1 A and h_FE ≥ 5 k, required I_B ≤ 0.2 mA. A 10 kΩ resistor from 3.3 V yields ~0.33 mA base current, ensuring saturation while staying within GPIO sink/source limits.

Does ZTX601STOB require a heatsink in 1 A continuous operation?

At 25°C ambient and P_tot = 1 W, the TO-92 package's thermal resistance (R_θJA) ≈ 175°C/W implies ΔT ≈ 175°C - exceeding max T_j. A minimal copper pad (≥1 cm²) is mandatory; for sustained 1 A, a low-profile heatsink or forced airflow is recommended to hold T_j ≤ 150°C.

How does ZTX601STOB's Darlington configuration affect switching speed compared to a single transistor?

The Darlington structure increases storage time and reduces f_T versus single transistors - resulting in t_off = 2.2 µs (vs. ~0.2 µs for comparable singles). This limits practical PWM frequency to ≤100 kHz but improves DC gain stability and reduces base drive sensitivity in noisy environments.