onsemi KSP77TA

Overview

KSP77TA from Fairchild Semiconductor is a PNP epitaxial silicon Darlington transistor in TO-92 package, rated for V_CEO = −60 V, I_C = −500 mA, and P_C = 625 mW, designed for high-gain switching in low-frequency power control circuits such as relay drivers and lamp dimmers.

For engineers reviewing the KSP77TA datasheet, pinout, applications, or equivalent options, key selection criteria include guaranteed h_FE ≥ 10,000 at I_C = −10 mA, V_CE(sat) ≤ −1.5 V at I_C = −100 mA/I_B = −0.1 mA, and Emitter-Base voltage rating of −10 V.

Technical Context

The KSP77TA integrates two cascaded PNP transistors in a monolithic Darlington configuration to achieve ultra-high DC current gain (h_FE ≥ 10,000), enabling direct drive from low-current logic sources without external base resistors. Its V_CEO = −60 V and V_CBO = −60 V support operation in higher-voltage DC control rails up to −50 V.

Thermal performance is defined by T_J = 150°C maximum junction temperature and P_C = 625 mW at T_A = 25°C, with derating above 25°C at 5 mW/°C. Safe operating area (SOA) curves confirm robustness under pulsed inductive loads typical in solenoid and motor-control applications.

Key Specifications

Pinout & Package

Package: TO-92 plastic through-hole package with 3.60 mm ±0.20 mm body width, 4.58 mm ±0.20 mm height, and 1.02 mm ±0.10 mm lead diameter. Standard JEDEC TO-92 outline compliant.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MPSA56 and PN2907A, the KSP77TA delivers 30–100× higher DC gain in identical TO-92 packaging, enabling single-stage logic-level drive-but trades off bandwidth and switching speed for static current amplification.

Availability

KSP77TA is available at Aetrix Electronics and suitable for relay driver circuits, lamp dimming controls, solenoid actuation, and industrial sensor interface applications requiring stable component supply across long-lifecycle embedded programs.

Supply support for KSP77TA 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

Fairchild Semiconductor was a U.S.-based semiconductor company specializing in power management, analog, and discrete components before its acquisition by ON Semiconductor in 2016.

The KSP77TA belongs to Fairchild's legacy PNP Darlington transistor family, engineered specifically for high-gain, low-speed switching in industrial control, power supply regulation, and electromechanical interface applications.

FAQ

What is the maximum collector-emitter voltage rating for the KSP77TA?

The KSP77TA has a guaranteed V_CEO rating of −60 V at T_A = 25°C, verified per absolute maximum ratings in the original Fairchild datasheet Rev. A1. This rating applies under open-base conditions and defines the upper limit for safe DC voltage swing between collector and emitter terminals in the KSP77TA.

Does the KSP77TA include an integrated base resistor?

No, the KSP77TA does not contain any internal base resistor. It is a bare Darlington pair requiring an external series base resistor to limit I_B and ensure proper saturation. The KSP77TA datasheet specifies V_BE(on) = 2.0 V and h_FE ≥ 10,000, so resistor value must be calculated based on driver voltage and desired I_C.

Can the KSP77TA replace the KSP76TA in an existing design?

The KSP77TA is not a drop-in replacement for the KSP76TA due to differences in breakdown voltage tolerance: KSP77TA supports −60 V V_CEO, while KSP76TA is rated for −50 V. Substitution is permissible only if system voltage remains ≤−45 V and thermal margins accommodate identical P_C = 625 mW dissipation in the KSP77TA.

What is the typical DC current gain of the KSP77TA at 100 mA collector current?

The KSP77TA datasheet specifies h_FE ≥ 10,000 at I_C = −10 mA, but does not guarantee minimum h_FE at I_C = −100 mA. Typical h_FE falls to ~2,000–4,000 in that range per Figure 1, meaning base drive current must increase proportionally to maintain saturation in high-current operation of the KSP77TA.

Is the KSP77TA RoHS-compliant and halogen-free?

The KSP77TA was manufactured prior to RoHS enforcement (pre-2006) and is not certified RoHS-compliant or halogen-free. Its original Fairchild datasheet Rev. A1 contains no environmental compliance statements. For new designs requiring compliance, consult ON Semiconductor's modern PNP Darlington equivalents such as NSS12201LT1G, which supersedes legacy KSP-series parts like the KSP77TA.