Diodes Incorporated ZDT6705TC

Overview

ZDT6705TC from Diodes Incorporated is a complementary medium-power dual Darlington transistor pair in SM-8 (SOT-223-8) package, integrating one NPN (V_CEO = 120 V, I_C = 1 A) and one PNP (V_CEO = −120 V, I_C = −1 A) die. It delivers h_FE ≥ 2000 at I_C = 50 mA and supports switching applications requiring matched gain and thermal coupling, such as linear power regulators and motor driver half-bridges.

For engineers reviewing the ZDT6705TC datasheet, ZDT6705TC pinout, ZDT6705TC application, or ZDT6705TC equivalent, key selection criteria include verified dual-die thermal resistance (45.5 °C/W with both transistors active), guaranteed V_CE(sat) ≤ 1.5 V (NPN) / ≤ −2.5 V (PNP) at I_C = 1 A, and confirmed SM-8 lead frame layout with isolated emitter terminals for independent bias control.

Technical Context

The ZDT6705TC implements a monolithic dual-die Darlington configuration with electrically isolated NPN and PNP transistors sharing a common thermal substrate. Each transistor features built-in base-emitter shunt resistors (not explicitly stated but implied by Darlington architecture and saturation voltage behavior), enabling direct TTL/CMOS drive without external base resistors in low-speed switching.

Its SM-8 package provides two independent emitter terminals (E1, E2), separate base connections (B1, B2), and shared collector pads (C1/C2 per device), supporting complementary push-pull output stages where emitter-follower or common-emitter topologies require independent emitter referencing and thermal tracking between devices.

Key Specifications

Pinout & Package

Package: SM-8 (8-lead SOT-223 variant), thermally enhanced with exposed die pad; pin 1–8 assigned as C1, C1, C2, C2, B1, E1, B2, E2 - physically arranged to support symmetrical PCB layout of complementary pairs.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ZXBD3001DN8TC and MBT3904DW1T1G, ZDT6705TC uniquely offers matched NPN/PNP characteristics at 120 V/1 A with Darlington gain ≥2000, making it irreplaceable in thermally coupled linear regulator and Class AB audio output designs requiring symmetry and low base drive.

Availability

ZDT6705TC is available at Aetrix Electronics and suitable for linear voltage regulators, DC motor half-bridge drivers, and audio power amplifier output stages requiring stable component supply across extended temperature ranges and multi-year production cycles.

Supply support for ZDT6705TC 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 since 1959.

ZDT6705TC belongs to Diodes' ZDT series of complementary Darlington transistors, engineered specifically for thermally matched, high-gain, medium-power linear and switching applications where dual-die integration improves stability and reduces board space.

FAQ

What is the maximum safe operating current for each transistor in ZDT6705TC under continuous DC conditions?

The absolute maximum continuous collector current is 1 A for the NPN and −1 A for the PNP transistor, provided the PCB layout includes at least 2 inches² of 2-ounce copper per device and ambient temperature remains ≤25°C. Derating is required above 25°C at 22 mW/°C when both dies are active, limiting usable current to ~0.75 A at 75°C ambient.

Does ZDT6705TC include internal base-emitter resistors?

No, ZDT6705TC does not integrate base-emitter shunt resistors. Its Darlington structure relies on externally applied base current; typical drive uses 1–10 mA base current depending on load, with V_BE(sat) = 1.8 V (NPN) and −1.8 V (PNP) confirming standard bipolar base junction behavior without integrated bias networks.

Can ZDT6705TC be used in parallel configurations to increase current capacity?

Parallel operation is not recommended. The two dies share a common thermal substrate but lack emitter ballasting or matched dynamic parameters for current sharing. Uneven thermal coupling and h_FE variation between NPN and PNP sections can cause current hogging; discrete current-sharing resistors would negate the benefit of the integrated dual-die package.

How does the SM-8 package of ZDT6705TC differ from standard SOT-223?

ZDT6705TC uses SM-8, an 8-lead variant of SOT-223 with doubled collector leads (C1/C1, C2/C2) and separate emitter terminals (E1, E2). Unlike standard 4-lead SOT-223, SM-8 supports independent emitter referencing and higher power dissipation (2.75 W vs. ~1.5 W) via optimized internal leadframe geometry and dual thermal paths to the exposed pad.