Diodes Incorporated ZDT605TA

Overview

ZDT605TA from Diodes Incorporated is a dual NPN medium-power Darlington transistor pair in SM-8 (SOT-223-8) package, rated for V_CEO = 120 V, I_C = 1 A per die, and h_FE ≥ 2000 at I_C = 50 mA - used in high-gain switching and linear amplification stages of industrial power supplies and relay drivers.

For engineers reviewing the ZDT605TA datasheet, ZDT605TA pinout, ZDT605TA application, or ZDT605TA equivalent, key selection criteria include guaranteed h_FE ≥ 2k at low drive current, dual-die thermal derating (22 mW/°C when both active), and verified V_CE(sat) ≤ 1.5 V at I_C = 1 A / I_B = 1 mA - critical for efficient base-driven load control.

Technical Context

The ZDT605TA integrates two independent NPN Darlington transistors on a single SM-8 substrate, each with built-in base-emitter resistors omitted - requiring external base drive. Its Darlington configuration delivers high DC current gain (h_FE up to 100k at low I_C) while maintaining V_CEO = 120 V and f_T = 150 MHz at I_C = 100 mA / V_CE = 10 V.

Thermal design must account for asymmetric dissipation: P_tot = 2.25 W with one die active, rising to 2.75 W only if both die operate equally - junction-to-ambient R_θJA is 55.6 °C/W (single) and 45.5 °C/W (dual), measured on 2-inch² PCB copper.

Key Specifications

Pinout & Package

Package: SM-8 (8-lead SOT-223 variant), surface-mount, thermally enhanced with exposed drain pad (shared between both transistors).

Key Features

Applications

Equivalent & Alternatives

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

Compared with ZTX605 and MBT3904DW1T1G, the ZDT605TA uniquely delivers dual-channel Darlington gain (h_FE ≥ 2k) at 120 V rating in one SM-8 package - eliminating layout complexity and thermal mismatch inherent in discrete pairing or low-voltage alternatives.

Availability

ZDT605TA is available at Aetrix Electronics and suitable for industrial relay drivers, DC motor direction controllers, linear voltage regulators, and high-voltage LED string switches requiring stable component supply and long-lifecycle support.

Supply support for ZDT605TA 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 Europe.

The ZDT605TA belongs to Diodes' high-voltage bipolar transistor product line, engineered specifically for industrial control applications demanding robustness, high DC gain, and reliable operation above 100 V.

FAQ

What is the maximum safe continuous collector current per transistor in ZDT605TA?

The absolute maximum continuous collector current is 1 A per transistor at T_amb = 25°C with adequate PCB copper (2-inch²). Derating is required above 25°C: 18 mW/°C per active die. At 70°C ambient, max I_C drops to ~820 mA per transistor to maintain T_j ≤ 150°C.

Does ZDT605TA include built-in base-emitter resistors?

No. The ZDT605TA contains two bare Darlington pairs without integrated base resistors. External base current must be supplied directly to B1 and B2 pins - typical drive is 1 mA per transistor for 1 A collector current, with V_BE(sat) = 1.8 V confirmed at that condition.

Can ZDT605TA be used in parallel configurations for higher current?

Not recommended. The two transistors share a common thermal pad but have independent dies; mismatched h_FE and V_BE curves cause unequal current sharing. For >1 A loads, use external emitter resistors (0.1 Ω) or select a single higher-rated device like ZXTN25012E.

What is the meaning of "SM-8" package designation for ZDT605TA?

SM-8 is Diodes Incorporated's proprietary 8-lead variant of the SOT-223 outline, featuring two isolated transistor die, shared thermal pad, and pinout optimized for dual-channel PCB layout. It is not compatible with standard SOT-223-3 or SOT-223-5 footprints due to additional leads and spacing.