KSC945 - NPN 50V 150mA 300MHz TO-92 BJT | onsemi
Référence : KSC945 ✓ Actif| Qté | Prix unitaire | Total |
|---|---|---|
| 1 | $0.45 | $0,45 |
| 10 | $0.38 | $3,80 |
| 100 | $0.24 | $24,00 |
| 500 | $0.18 | $90,00 |
| 1 000 | $0.14 | $140,00 |
KSC945 Présentation
A bipolar junction transistor is a three-terminal current-controlled semiconductor device that amplifies or switches electronic signals. Within the component hierarchy, the KSC945 belongs to the small-signal BJT family -> discrete transistor -> semiconductor device, complementing the KSA733 PNP device for push-pull stages. Small-signal NPN transistors like the KSC945 remain staples of analog design because of their low cost, predictable gain grades, and forgiving through-hole assembly.
Key features include VCBO of 60 V, VCEO of 50 V, VEBO of 5 V, fT of 300 MHz (typical), and gain grading via O, Y, and G hFE suffixes for design selectivity. The device is specified for audio frequency amplifier and high-frequency oscillator service, and its lead configuration is 1. Emitter, 2. Base, 3. Collector; the "-C" suffix denotes a center-collector variant (1. Emitter, 2. Collector, 3. Base).
Technically, the KSC945 uses an epitaxial silicon process delivering a high current-gain bandwidth product, which keeps loop gain healthy at audio frequencies and supports oscillators into the tens of MHz. The 300 MHz fT provides margin for RF buffer and crystal oscillator stages, while the 50 V VCEO accommodates 24 V and higher rail analog circuitry.
Typical applications include preamplifier and tone-stack gain stages in audio equipment, crystal and LC oscillators, LED and relay driver buffers, and vintage-audio restoration where the KSC945 substitutes the classic 2SC945. Its TO-92 package suits prototyping and low-volume industrial builds.
Design consideration: keep dissipation below the 250 mW limit - at FR-4 reference board size (76 mm x 114 mm x 1.57 mm) per the datasheet derating curve, and always verify hFE grade (O/Y/G) when gain-critical circuits are involved.
This page synthesizes distributor pricing, drop-in alternatives, gain-grade comparisons, and practical design notes not found in the manufacturer datasheet.
Alternatives de remplacement direct pour KSC945 — même boîtier, compatible broche à broche. Les références à boîtier différent nécessitant une retouche du PCB sont exclues.
Outil de comparaison rapide — sélectionnez des références alternatives pour une comparaison côte à côte :
KSC945YTA
✅ Remplacement direct📋 Alternative de référence (hors catalogue)
KSC945O
✅ Remplacement direct📋 Alternative de référence (hors catalogue)
KSC945G
✅ Remplacement direct📋 Alternative de référence (hors catalogue)
KSC945C
✅ Remplacement direct📋 Alternative de référence (hors catalogue)
2SC945
✅ Remplacement direct📋 Alternative de référence (hors catalogue)
BC537
✅ Remplacement direct📋 Alternative de référence (hors catalogue)
KTC9014
✅ Remplacement direct📋 Alternative de référence (hors catalogue)
KSC945 Valeurs maximales et caractéristiques électriques
| Polarity | NPN |
| Technology | NPN Epitaxial Silicon |
| Tension collecteur-base (Vcbo) | 60 V |
| Tension collecteur-émetteur (Vceo) | 50 V |
| Tension émetteur-base (Vebo) | 5 V |
| Courant de collecteur (Ic) | 150 mA |
| Power Dissipation (PD) | 250 mW |
| Gain Bandwidth Product (fT) | 300 MHz (typical) |
| Complementary Pair | KSA733 (PNP) |
| hFE Groups | O / Y / G gain grades |
| Boîtier | TO-92-3 (Through Hole) |
| Pin Configuration | 1. Emitter, 2. Base, 3. Collector (-C suffix: center collector) |
| Type de montage | Through Hole |
| Typical Applications | Audio frequency amplifier, high-frequency oscillator |
| Reference PCB for Derating | FR-4, 76 mm x 114 mm x 1.57 mm, minimum land pattern |
Configuration des broches de KSC945
| Broche 1 | Emitter — Emitter terminal (E-B-C lead order, flat side facing viewer) |
| Broche 2 | Base — Base control terminal |
| Broche 3 | Collector — Collector terminal; -C suffix variants use center collector (E-C-B) |
Applications typiques
KSC945 convient pour 6 applications: Audio Frequency Amplifier Stages, High-Frequency Oscillators, Vintage Audio Restoration, LED and Relay Driver Buffers, Analog Signal Processing in Musical Instruments, Sensor and Microcontroller Interface Front Ends.
Audio Frequency Amplifier Stages
The KSC945 is explicitly characterized for audio frequency amplifier service in the onsemi datasheet, and its 300 MHz typical fT keeps loop gain high across the entire audio band, so distortion stays low even with generous negative feedback. In preamplifier, tone-control, and phono stages it is biased at low collector currents of 1-5 mA, far below the 150 mA rating, preserving linearity and low noise. Its hFE grading into O, Y, and G groups lets designers select a narrow gain window so differential and push-pull pairs stay balanced without trimpots. Because it is complementary to the KSA733 PNP, symmetric NPN/PNP stages can be built from datasheet-matched pairs, simplifying bias design and improving thermal tracking in discrete audio signal chains.
Recommandé
High-Frequency Oscillators
Per the onsemi datasheet, the KSC945 is specified for high-frequency oscillator applications alongside audio amplification. The 300 MHz typical gain-bandwidth product gives substantial unity-gain margin for crystal oscillators, Colpitts and Hartley LC oscillators, and RF buffer stages operating from a few MHz into the low-VHF range. In a Colpitts topology, the KSC945 is typically biased at 2-10 mA where its fT remains near the typical value, and the 50 V VCEO allows oscillator stages on 24 V or 28 V rails common in radio equipment. The 5 V VEBO limit should be respected in high-drive oscillators by limiting base excursion. Through-hole TO-92 construction also simplifies prototyping of oscillator boards and frequency-standard modules used in test and communications equipment.
Recommandé
Vintage Audio Restoration
The KSC945 is the modern onsemi continuation of the classic 2SC945 used throughout Japanese hi-fi and instrument amplifiers from the 1970s and 1980s, making it the standard replacement in vintage-audio restoration work. Forum and cross-reference discussions (diyAudio, Hudson Valley HiFi substitution tables) repeatedly identify the KSC945 lineage as the faithful modern equivalent for 2SC945 positions. Its E-B-C lead order and hFE grade system require verification against the original part's pin convention during replacement, since some 2SC945 variants used E-C-B ordering. With 50 V VCEO and 150 mA IC, it covers the bias points of tone, phono, and driver stages in these designs, and matched O/Y/G grades allow original gain balance to be preserved across channels.
Recommandé
LED and Relay Driver Buffers
With a 150 mA collector current rating and 50 V VCEO, the KSC945 serves as a low-side driver for indicator LEDs, small relays, and optocoupler input stages in industrial and test equipment. Estimated: at IC = 50 mA and VCE(sat)-class operation, device dissipation stays in the tens of milliwatts, far below the 250 mW limit, so no thermal design effort is needed. A base resistor sized for forced beta of 10-20 gives hard switching and clean saturation. The 50 V rating covers 24 V industrial rails with margin that 20-25 V class transistors lack, and the TO-92 through-hole package withstands hand soldering during panel wiring, making it convenient for maintenance, prototyping, and low-volume control board builds.
Recommandé
Analog Signal Processing in Musical Instruments
Guitar pedals, synthesizers, and mixing consoles rely heavily on small-signal NPN transistors for input buffers, gain stages, and discrete op-amp cores. The KSC945's 300 MHz fT and audio-banded gain make it popular in this space, and its availability in graded hFE bins supports the gain-matching that parametric and fuzz circuits require. Hobbyist and builder communities (for example diyAudio and diystompboxes threads) commonly source KSC945 or its equivalents when original 2SC945-family stock runs out. The 50 V VCEO covers 9-24 V pedal supplies with wide margin, and the 250 mW dissipation limit is never approached at typical stage currents of 0.5-2 mA. Through-hole packaging suits the hand-assembled, socketed construction typical of boutique effects hardware.
Recommandé
Sensor and Microcontroller Interface Front Ends
Discrete NPN front ends remain useful ahead of ADC inputs and microcontroller GPIO in cost-sensitive designs. The KSC945 can be configured as a common-emitter preamplifier for photodiodes, microphones, or thermistor bridge signals, with its 300 MHz bandwidth comfortably exceeding any baseband sensor requirement and its 50 V VCEO tolerating inductive sensor kickback better than 15-25 V class devices. When driven from 3.3 V or 5 V MCU logic, a base series resistor sets the operating point, and the hFE grade (Y or G groups) should be selected to guarantee saturation at the available base current. Its through-hole TO-92 package also makes it easy to replace during bench bring-up and calibration of prototype sensor boards.
Recommandé
Récapitulatif des produits recommandés
Données de référence d'ingénierie pour KSC945 — comparaison, recommandations de conception et informations de conformité.
Guide de sélection
Comparaison avec les alternatives
| Paramètre | Ce produit | KSC945YTA | 2SC945 | BC537 | KTC9014 |
|---|---|---|---|---|---|
| Package | TO-92-3 (Through Hole) | TO-92-3 - same | TO-92 - same footprint | TO-92 - same footprint | TO-92 - same footprint |
| Brand | onsemi | onsemi | KEC | NXP Semiconductors | KEC |
| VCEO | 50 V | 50 V | 50 V | 45 V | 50 V |
| Collector Current | 150 mA | 150 mA | 150 mA | 1 A | 150 mA |
| fT (typical) | 300 MHz | 300 MHz | 250 MHz | 100 MHz | 120 MHz |
| Power Dissipation | 250 mW | 250 mW | 250 mW | 625 mW | 150 mW |
| Pin Order | E-B-C | E-B-C | E-C-B (verify per maker) | C-B-E (verify per maker) | E-C-B |
| Gain Grading | O / Y / G hFE groups | Y grade | O / Y / GR grades | -6/-10/-16 suffix grades | O / Y / GR grades |
Principaux différenciateurs
- Highest small-signal bandwidth in the comparison set (vs BC537)
- True complement pairing (vs KTC9014)
- Graded hFE bins for matched-stage design (vs 2SC945)
Notes de conception
The KSC945 is rated 250 mW total dissipation, derated above 25 C ambient per the datasheet curve, which is referenced to an FR-4 PCB of 76 mm x 114 mm x 1.57 mm with minimum land patterns. Estimated: a stage dissipating 100 mV x 100 mA = 10 mW is trivially safe, but a 5 V x 40 mA linear stage reaches 200 mW - near the limit on small boards. Keep VCE x IC products below roughly half the rating in enclosed, high-ambient products.
Never substitute KSC945 and KSC945C (center collector) on the same footprint without checking lead order - the -C suffix moves the collector to the center lead (E-C-B instead of E-B-C) and will destroy the transistor on power-up if swapped. Likewise, cross-brand equivalents such as 2SC945 and KTC9014 frequently use E-C-B ordering. Mark the pinout on the silkscreen and verify with a meter before soldering replacement parts into vintage or mixed-manufacturer boards.
Select hFE grade deliberately: the O, Y, and G suffixes are gain bins, and using a random grade in a gain-critical stage shifts bias point and stage gain. For differential pairs and push-pull complements with the KSA733, order parts from the same grade and, ideally, the same date code. In oscillator service, bias the collector current where the 300 MHz fT is realized (per datasheet fT-vs-IC curve) rather than at starvation currents, or oscillation margin will suffer.
Informations de conformité
Compliance attributes were not stated in the retrieved web data; confirm RoHS/REACH/lead-free status on the onsemi product page before ordering for regulated markets.
