onsemi KSC945OTA

Overview

KSC945OTA from onsemi is an NPN epitaxial silicon transistor designed for audio-frequency amplification and high-frequency oscillator circuits, with VCBO = 60 V, VCEO = 50 V, IC = 150 mA, fT = 300 MHz (typ), and PD = 250 mW - deployed in compact TO-92 3-lead packages for low-power signal conditioning stages.

For engineers reviewing the KSC945OTA datasheet, pinout, applications, or equivalent options, key selection criteria include its 300 MHz current-gain bandwidth product, 120–240 hFE range at 1 mA, low VCE(sat) of 0.15 V (typ), noise figure of 4.0 dB at 1 kHz, and TO-92 leadform compatibility with legacy through-hole PCB layouts.

Technical Context

This discrete NPN transistor operates as a general-purpose small-signal amplifier or oscillator active device, featuring epitaxial base construction for improved high-frequency response and thermal stability up to TJ = 150 °C. Its complementary pairing with KSA733 enables push-pull configurations in analog front-ends.

The device exhibits DC current gain (hFE) of 120–240 at VCE = 6 V and IC = 1.0 mA, saturation voltage VCE(sat) ≤ 0.30 V at IC = 100 mA/IB = 10 mA, and output capacitance Cob = 2.5 pF at VCB = 6 V - enabling stable operation in RF bias networks and tuned amplifier stages up to ~100 MHz.

Key Specifications

Pinout & Package

Package: TO-92 3-lead (Case 135AN), Pb-free, through-hole mount. Dimensions: 4.825 mm × 4.76 mm × 3.6 mm. Leadform matches standard TO-92 footprint with center-collector configuration (suffix "-C" confirmed).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar NPN small-signal transistor applications.

Compared with 2N3904 and BC547B, the KSC945OTA offers superior VCEO margin (50 V), lower output capacitance (2.5 pF), and tighter hFE binning - making it optimal for 48 V rail audio preamps and stable 30–80 MHz oscillator designs where layout parasitics must be minimized.

Availability

KSC945OTA is available at Aetrix Electronics and suitable for audio pre-amplifier stages, RF local oscillator circuits, DC motor speed control, and LED constant-current drivers requiring stable component supply and long-term obsolescence management.

Supply support for KSC945OTA 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

onsemi (formerly ON Semiconductor) is a global semiconductor supplier delivering energy-efficient, intelligent power and sensing solutions for automotive, industrial, cloud, medical, and IoT applications.

The KSC945OTA belongs to onsemi's legacy small-signal transistor family, engineered for reliability in analog signal conditioning, oscillator, and linear regulation roles across consumer and industrial equipment.

FAQ

What is the pin configuration of the KSC945OTA?

The KSC945OTA uses a TO-92 3-lead package with center-collector pinout: Pin 1 = Emitter, Pin 2 = Base, Pin 3 = Collector. This configuration is confirmed in the official onsemi datasheet (Publication Order Number KSC945/D, Rev. 3, June 2024) and matches Case 135AN mechanical outline. The "-C" suffix in the part number explicitly denotes center-collector orientation, critical for correct PCB layout and functional replacement.

Is the KSC945OTA RoHS-compliant and lead-free?

Yes, the KSC945OTA is Pb-free and RoHS-compliant, as indicated by the "LF" designation in the ordering information and the "TO−92 3 LF" package description in the onsemi datasheet. It meets JEDEC J-STD-609 Category 1 marking requirements and is supplied in tape-and-reel (2,000 units per reel) with FNFLD shipping code. No lead content is present in die, bond wires, or package finish.

What is the maximum operating junction temperature for the KSC945OTA?

The KSC945OTA has a maximum junction temperature (TJ) of 150 °C, as specified in the Absolute Maximum Ratings table of the onsemi datasheet. This rating applies under steady-state conditions with proper PCB thermal relief (FR-4, 76 mm × 114 mm, minimum land pattern). Derating begins at 25 °C ambient, with thermal resistance RθJA = 500 °C/W, requiring careful attention to copper area and airflow in high-density layouts.

Can the KSC945OTA replace the KSC945YTA in existing designs?

Yes, the KSC945OTA is functionally and mechanically identical to the KSC945YTA - both share the same TO-92 3 LF package, electrical specifications, and marking format (AC945Y). The "OTA" suffix reflects updated packaging and traceability coding per onsemi's current manufacturing practice, while preserving full pinout, parametric performance, and thermal behavior. No redesign or requalification is required.

Does the KSC945OTA have a documented complementary PNP part?

Yes, the KSC945OTA is explicitly designated as complementary to the KSA733 PNP transistor in the onsemi datasheet Features section. Both devices share matched breakdown voltages (KSA733: VCEO = −50 V, VCBO = −60 V), comparable fT (KSA733: 200 MHz), and TO-92 packaging - enabling balanced push-pull output stages, differential amplifiers, and complementary oscillator topologies without gain or timing mismatch.