What Series Do KOA Resistors Have? A Complete Guide to the KOA Resistor Product Lineup
Founded in 1940 in Nagano, Japan, KOA Corporation has spent more than eight decades focusing exclusively on resistor technology. Its lineup spans thick film, thin film, metal plate and wirewound constructions, covering everything from 01005 micro chips to high-power shunts. So what series do KOA resistors actually include, and how do they differ in features, applications and market positioning? This guide breaks it down systematically.
What Series Do KOA Resistors Have? A Complete Guide to the KOA Resistor Product Lineup
In the passive components industry, KOA resistors are well known for their broad portfolio and proven reliability. Founded in 1940 in Nagano, Japan, KOA Corporation has spent more than eight decades focusing exclusively on resistor technology. Its lineup spans thick film, thin film, metal plate and wirewound constructions, covering everything from 01005 micro chips to high-power shunts. So what series do KOA resistors actually include, and how do they differ in features, applications and market positioning? This guide breaks it down systematically.
1. General-Purpose Thick Film Chip Resistors: RK73 Series
RK73 is the backbone of the KOA resistor family and is divided into four sub-series: RK73B (general purpose, ±2% and ±5%), RK73H (precision, ±0.5% and ±1%, TCR ±100ppm/K), RK73G (ultra precision down to ±0.25%) and RK73Z (zero-ohm jumpers, max. 50mΩ). Covering case sizes from 01005 to 2512 with power ratings up to 2W, and AEC-Q200 qualified in nearly all sizes, the RK73 family is the default choice for consumer electronics, power adapters, home appliances and automotive electronics — a cost-effective standard product line.
2. High-Reliability Ultra-Precision Thick Film: RS73 Series
RS73 is a differentiated KOA resistor series that delivers "thin-film performance at thick-film cost": ±0.1% initial tolerance and ±25ppm/K TCR, excellent long-term stability, and better ESD robustness than comparable thin-film parts. It targets industrial control, measurement instruments and telecom infrastructure, where precision and reliability must be balanced against budget.
3. Thin Film High-Precision Resistors: RN73 and WN73 Series
On the thin-film side, KOA resistors are led by RN73R/RN73H, offering tolerances down to ±0.05%, TCRs as tight as ±5ppm/K and minimal drift over thousands of hours — ideal for precision dividers, reference circuits and medical equipment. RN73H adds an internal SiO₂ moisture barrier for harsh automotive environments such as engine compartments. For higher power, the wide-terminal WN73H reaches 1W in a 0612 package. KOA also offers silicon-based specialties such as the RTY precision divider in SOT-23 and the HVD high-voltage divider network rated up to 1000V.
4. Anti-Surge and Anti-Pulse Resistors: SG73 and WG73 Series
Power inputs and lightning-protection circuits face heavy transient energy. The KOA resistor answer is the SG73 family: SG73 (general anti-surge), SG73P (precision anti-pulse), SG73S (anti-surge precision), SG73G (ultra precision ±0.25% with pulse withstanding) and HSG73P (enhanced heat resistance). The wide-terminal WG73 achieves 1W in a 1020 package with superior pulse handling. Typical uses include switching power supplies, LED drivers, EV charging piles and security equipment.
5. High-Voltage Resistors: HV73 and HV73V Series
Thanks to special inner electrode materials and internal insulation, HV73 handles 800V working voltage in 1206 and up to 3000VDC in 2512, with resistance values reaching 100MΩ. HV73V is the AEC-Q200 qualified automotive version with improved temperature-cycling performance. Both serve voltage dividers and sensing circuits in inverters, servo drives, photovoltaic systems and EV battery management.
6. Wide-Terminal High-Power Resistors: WK73 Series
WK73R places the terminations on the long sides of the chip, shortening the current path and improving heat dissipation: 1.5W in 0612 and up to 3W in 1225 — roughly twice the power of a standard part of the same footprint — while also reducing solder-joint stress under thermal cycling. It fits power modules and motor drives where continuous high load meets space constraints.
7. Low-Ohm Current Sense Resistors and Power Shunts
Current sensing is another strength of KOA resistors. SR73 and UR73V go down to 10mΩ, with UR73V2A delivering 0.5W and TCR as low as ±75ppm/K in 0805. The wide-terminal WK73S handles up to 4W in 1225. Metal-plate power shunts such as PSL2, PSJ2 and PSG4 push power ratings to 8–12W with resistance down to 0.2mΩ and operating temperatures up to +175°C, serving battery management, server power and high-current fast charging.
8. Anti-Sulfur Resistors: RT Series
In sulfur-rich environments, conventional silver-electrode chips fail open due to sulfuration. KOA is a leader in anti-sulfur chip resistors: its RT family (RK73B-RT, RK73H-RT, RS73-RT, SG73P-RT, SR73-RT and more) uses highly sulfuration-proof electrode materials, passes ASTM-B809 testing, and spans nearly every category — general purpose, precision, wide terminal, high voltage, anti-surge and current sense — making it the first choice for mining equipment, outdoor telecom and other harsh settings.
9. Leaded and Special Resistors
Beyond SMD parts, KOA resistors include a full leaded lineup — MOS metal oxide film resistors, SPR/CW wirewound and power types, fusible resistors — plus thermistors and varistors such as the NV73S multilayer varistor handling surges up to 6,000A, addressing power supply, safety and overvoltage protection needs.
10. Recommended Supplier
With such an extensive portfolio, selecting the right KOA resistor often means weighing precision, power, pulse handling and sulfur resistance together — and a well-stocked distributor with real technical support makes that much easier. Shenzhen Shunhai Technology Co., Ltd. has long specialized in KOA and other Japanese-brand chip resistors, keeping mainstream series such as RK73, SG73, HV73 and WK73 in stock, and providing selection guidance, samples and volume supply. It is a trustworthy sourcing partner for KOA resistors.
Conclusion: From the general-purpose RK73 to the high-precision RN73, from the anti-surge SG73 to the anti-sulfur RT family, KOA resistors form a complete series matrix covering consumer, automotive, industrial and new-energy applications. Understanding how each series is positioned is the key to optimizing performance, reliability and cost in your design.