onsemi 2SC3708T

Overview

2SC3708T from SANYO Semiconductor is an NPN epitaxial planar silicon transistor designed for low-frequency driver and audio power amplifier applications. It delivers V_CEO = 80 V, I_C = 500 mA, P_C = 600 mW, f_T = 120 MHz, and V_CE(sat) = 0.16 V at I_C = 400 mA / I_B = 40 mA - enabling robust switching and linear amplification in compact audio output stages.

For engineers reviewing the 2SC3708T datasheet, pinout, applications, or equivalent options, key selection criteria include its high breakdown voltage, DC current gain (h_FE = 100–400 at 50 mA), saturation performance under pulsed load, thermal stability up to T_j = 150°C, and TO-92-compatible package footprint.

Technical Context

The 2SC3708T employs FBET (Flat Base Epitaxial Transistor) process technology to achieve tight parameter distribution and stable h_FE across temperature. Its design targets low-frequency linear operation with controlled saturation characteristics and low output capacitance (C_ob = 5 pF at V_CB = 10 V).

It operates as a single-element NPN bipolar junction transistor with fixed emitter-collector polarity and base-controlled current amplification. No integrated biasing, protection, or digital logic is present - functionality is strictly analog current-controlled conduction per JEDEC TO-92 mechanical and electrical conventions.

Key Specifications

Pinout & Package

Package: TO-92 (3-lead plastic molded), lead material: tin-plated copper, standard JEDEC outline per SANYO drawing 7522-002. Dimensions: 4.0 mm × 5.0 mm × 4.0 mm (L×W×H), lead pitch 1.3 mm.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 2SC2274 and BC547C, the 2SC3708T provides superior voltage headroom and current drive for audio and motor control, while maintaining TO-92 compatibility - making it the optimal choice when both 80 V V_CEO and 500 mA I_C are required in a through-hole discrete solution.

Availability

2SC3708T is available at Aetrix Electronics and suitable for audio power amplifiers, low-frequency driver circuits, DC motor speed controllers, and relay/LED interface modules requiring stable component supply and long-term industrial availability.

Supply support for 2SC3708T 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

SANYO Semiconductor was a Japanese semiconductor manufacturer specializing in analog, power, and discrete devices before its acquisition by ON Semiconductor in 2011. Known for high-reliability audio and power transistors.

The 2SC3708T belongs to SANYO's general-purpose low-frequency bipolar transistor product line, engineered specifically for cost-sensitive yet performance-critical audio driver and linear amplification roles in consumer and industrial equipment.

FAQ

What is the maximum safe operating voltage for 2SC3708T?

The 2SC3708T has a guaranteed minimum collector-to-emitter breakdown voltage V(BR)_CEO of 80 V at I_C = 1 mA. For reliable long-term operation, the recommended maximum V_CE is 64 V (80% of rating) under continuous DC conditions. At elevated temperatures or with inductive loads, further derating is advised to avoid secondary breakdown.

Does 2SC3708T support complementary pairing with a PNP transistor?

Yes - the 2SC3708T is explicitly designed and characterized as the NPN complement to the 2SA1450 PNP transistor. Both share identical package dimensions, thermal characteristics, and matched gain/breakdown specifications, enabling symmetrical Class AB audio output stages with minimized thermal tracking error.

What is the typical DC current gain (h_FE) of 2SC3708T at 400 mA collector current?

At V_CE = 5 V and I_C = 400 mA, the 2SC3708T exhibits h_FE2 ≥ 60 (minimum), with typical values around 80–100. This lower-gain mode reflects intentional design for stable high-current operation, distinct from its 100–400 h_FE rating at 50 mA used for bias network design.

Can 2SC3708T be used in switching applications?

Yes - the 2SC3708T supports switching use with I_CP = 800 mA (pulse) and V_CE(sat) = 0.16 V (typ) at I_C/I_B = 400 mA/40 mA. Its f_T = 120 MHz allows clean turn-on/turn-off up to ~100 kHz PWM, though switching speed is limited by minority-carrier storage time inherent to standard bipolar construction.

Is 2SC3708T RoHS-compliant and halogen-free?

The original 2SC3708T datasheet (EN2217B, Nov 2009) predates full RoHS enforcement for legacy discretes and does not declare compliance status. Current Aetrix-supplied units meet RoHS Directive 2011/65/EU and JEDEC JS709C halogen-free requirements, verified via material declarations and XRF testing on production lots.