onsemi KSC2787YBU

Overview

KSC2787YBU from Fairchild Semiconductor is an NPN epitaxial silicon transistor designed for RF amplification, mixing, conversion, oscillation, and IF stages in FM/AM receivers. It features VCEO=30V, fT=300MHz (typ), Cob=2.0pF (typ), hFE=120–240 (Y-class), and TO-92S package for compact RF board layout.

For engineers reviewing the KSC2787YBU datasheet, pinout, applications, or equivalent options, key selection criteria include RF gain-bandwidth performance, low output capacitance for tuning stability, VCEO derating at elevated temperature, and Y-class hFE binning for consistent bias design in multi-stage amplifiers.

Technical Context

This transistor operates as a high-frequency small-signal amplifier with fT up to 300MHz under VCE=6V, IC=1mA conditions. Its low Cob (2.0pF typ) and tight hFE classification (Y: 120–240) support stable gain and predictable biasing in tuned RF circuits.

The device uses epitaxial base construction for improved frequency response and reduced base resistance. With VCEO=30V and IC=50mA max, it targets low-power RF front-end stages where thermal dissipation (PC=250mW) and junction temperature limits (TJ=150°C) constrain continuous operation.

Key Specifications

Pinout & Package

Package: TO-92S - 3-lead plastic through-hole package with 1.27 mm lead pitch, 4.00 mm body height, and compact footprint optimized for RF layout density.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 2SC3356 and MPSH10, the KSC2787YBU offers balanced VCEO/fT/Cob trade-offs for 30V-tolerant FM/AM designs, with Y-class hFE ensuring repeatable biasing-critical for multi-unit manufacturing where gain-matching reduces post-assembly calibration.

Availability

KSC2787YBU is available at Aetrix Electronics and suitable for FM/AM radio receivers, IF amplifier modules, RF oscillator circuits, and portable communication devices requiring stable component supply across long-lifecycle consumer electronics programs.

Supply support for KSC2787YBU 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 leading designer of discrete semiconductors and analog ICs, acquired by ON Semiconductor in 2016; its legacy RF transistor portfolio remains widely deployed in consumer audio and broadcast equipment.

The KSC2787YBU belongs to Fairchild's general-purpose RF transistor family targeting FM/AM receiver signal chains, emphasizing high fT, low Cob, and production-grade hFE binning for cost-effective, high-yield radio manufacturing.

FAQ

What is the hFE classification for KSC2787YBU?

The KSC2787YBU is Y-class binned, meaning its DC current gain (hFE) is guaranteed between 120 and 240 when measured at VCE=6V and IC=1mA. This tighter range compared to R (40–80) and O (70–140) classes allows more predictable base bias design in production RF amplifiers, reducing unit-to-unit gain variation without individual trimming. The KSC2787YBU datasheet specifies this classification explicitly in the hFE Classification table.

Can KSC2787YBU replace KSC2787OBU in a circuit?

Yes, the KSC2787YBU can replace KSC2787OBU electrically and mechanically, as both share identical absolute maximum ratings, package (TO-92S), pinout, and test conditions-but the YBU offers higher and tighter hFE (120–240 vs. 70–140). Circuits relying on minimum gain margins may see improved stability, though bias resistors may require minor adjustment. The KSC2787YBU maintains full pin compatibility and thermal characteristics of the original KSC2787 series.

What is the maximum operating frequency for KSC2787YBU in amplifier mode?

The KSC2787YBU achieves a typical current gain bandwidth product (fT) of 300 MHz at VCE=6V and IC=1mA, indicating usable gain up to approximately 100–150 MHz in practical common-emitter amplifier configurations. Its performance remains effective in FM band (88–108 MHz) and 10.7 MHz IF stages; operation beyond 200 MHz requires careful layout due to Cob=2.0pF and package parasitics. The KSC2787YBU datasheet confirms fT via Figure 5.

Is KSC2787YBU suitable for oscillator applications?

Yes, the KSC2787YBU is explicitly recommended for oscillator use in FM/AM systems per its original application note: "KSC2787 FM/AM RF AMP, MIX, CONV, OSC, IF". Its high fT (300 MHz typ), low VCE(sat) (0.08–0.3 V), and stable hFE support reliable start-up and low-distortion sinusoidal output in Colpitts and Hartley topologies. The KSC2787YBU's low Cob also suppresses unwanted phase shifts critical for oscillator loop stability.

What is the thermal resistance junction-to-ambient for KSC2787YBU?

The KSC2787YBU does not specify a published θJA value in its Rev. A2 datasheet; however, based on its TO-92S package geometry (4.00 mm height, 2.31 mm width) and 250 mW maximum collector power dissipation, typical θJA falls between 200–250°C/W under still-air conditions. Derating is required above 25°C ambient-e.g., maximum PC drops to ~180 mW at 70°C. The KSC2787YBU's TJ limit of 150°C must be respected in PCB layout with adequate copper pour near the emitter lead.