Bekijk alles

Raadpleeg de Engelse versie als onze officiële versie.Opbrengst

Europa
France(Français) Germany(Deutsch) Italy(Italia) Russian(русский) Poland(polski) Czech(Čeština) Luxembourg(Lëtzebuergesch) Netherlands(Nederland) Iceland(íslenska) Hungarian(Magyarország) Spain(español) Portugal(Português) Turkey(Türk dili) Bulgaria(Български език) Ukraine(Україна) Greece(Ελλάδα) Israel(עִבְרִית) Sweden(Svenska) Finland(Svenska) Finland(Suomi) Romania(românesc) Moldova(românesc) Slovakia(Slovenská) Denmark(Dansk) Slovenia(Slovenija) Slovenia(Hrvatska) Croatia(Hrvatska) Serbia(Hrvatska) Montenegro(Hrvatska) Bosnia and Herzegovina(Hrvatska) Lithuania(lietuvių) Spain(Português) Switzerland(Deutsch) United Kingdom(English)
Aziatisch-Pacifisch
Japan(日本語) Korea(한국의) Thailand(ภาษาไทย) Malaysia(Melayu) Singapore(Melayu) Vietnam(Tiếng Việt) Philippines(Pilipino)
Afrika, India en het Midden -Oosten
United Arab Emirates(العربية) Iran(فارسی) Tajikistan(فارسی) India(हिंदी) Madagascar(malaɡasʲ)
Zuid -Amerika / Oceanië
New Zealand(Maori) Brazil(Português) Angola(Português) Mozambique(Português)
Noord Amerika
United States(English) Canada(English) Haiti(Ayiti) Mexico(español)
HuisproductenPower Supplies - Board MountDC gelijkstroomconverters

DC gelijkstroomconverters

11,620 -producten gevonden

Product lijst

1...184185186187188189190...233
Vergelijken Beeld Deel # Fabrikant Beschrijving Inventaris ECAD -model RoHS doeltreffendheid Aantal uitgangen Beheersfuncties Current - Output (Max) Voltage - Input (Min) Voltage - Output 1 Voltage - Output 2 Voltage - Output 3 Voltage - Output 4 Voltage - Isolatie Goedkeuringsbureau Standaardnummer Base Productnummer Pakket montage Type Serie Temperatuur Size / Dimension Voltage - Input (Max) Type Kenmerken toepassingen Verpakking / doos Leverancier Device Pakket Vermogen (Watt) Aantal stuks
VE-J21-MZ Vicor Corporation DC DC CONVERTER 12V 25W Op voorraad3620 pcs 90% 1 - 2.08A 21V 12V - - - 3 kV - - VE-J21 Bulk Through Hole VE-J00™ (25W) -55°C ~ 100°C 2.28' L x 2.40' W x 0.50' H (57.9mm x 70.0mm x 12.7mm) 56V Isolated Module OCP, SCP ITE (Commercial) Half Brick - 25 W
PT500-66 TDK-Lambda Americas Inc DC DC CONVERTER 66V 528W Op voorraad5470 pcs 93% 1 - 8A 352.8V 66V - - - 3 kV - - - - Through Hole PT (500W) -20°C ~ 85°C (With Derating) 5.75" L x 3.39" W x 0.50" H (146.0mm x 86.0mm x 12.7mm) 367.2V Isolated Module Remote On/Off, OCP, OTP, OVP ITE (Commercial) 8-DIP Module - 528 W
VE-2N0-IW Vicor Corporation DC DC CONVERTER 5V 100W Op voorraad4100 pcs 90% 1 - 20A 36V 5V - - - 3 kV - - VE-2N0 Bulk Through Hole VE-200™ (100W) -40°C ~ 85°C 4.60' L x 2.40' W x 0.50' H (116.8mm x 61.0mm x 12.7mm) 76V Isolated Module OCP, OTP, OVP, SCP ITE (Commercial) Full Brick - 100 W
VE-911004B Vicor Corporation C 180/375/300 12V/ 22A Op voorraad4450 pcs - - - - - - - - - - - - - Bulk - * - - - - - - - - -
AEE02A12-49 Artesyn Embedded Power DC DC CONVERTER 5V 10W Op voorraad4430 pcs 81% 1 - 2A 9V 5V - - - 500 V - - - Bulk Through Hole AEE02 (10W) -25°C ~ 100°C 2.00" L x 1.00" W x 0.40" H (50.8mm x 25.4mm x 10.2mm) 18V Isolated Module - ITE (Commercial) 6-DIP Module - 10 W
VE-J10-EX Vicor Corporation DC DC CONVERTER 5V 75W Op voorraad3950 pcs 88% 1 - 15A 21V 5V - - - 3 kV - - VE-J10 Bulk Through Hole VE-J00™ (75W) -10°C ~ 100°C 2.28" L x 2.40" W x 0.50" H (57.9mm x 70.0mm x 12.7mm) 32V Isolated Module OCP, SCP ITE (Commercial) Half Brick - 75 W
MPM3810AGQB-Z Monolithic Power Systems Inc. 6V INPUT, 1.2A MODULESYNCHRONOUS Op voorraad38113 pcs - 1 - 1.2A 2.6V 0.312 ~ 0.72V - - - - - - - Tape & Reel (TR) Surface Mount Automotive, AEC-Q100 -40°C ~ 125°C 0.12" L x 0.10" W x 0.04" H (3.0mm x 2.5mm x 0.9mm) 6V Non-Isolated PoL Module Adjustable Output, Remote On/Off ITE (Commercial) 12-PowerVFQFN Module 12-QFN (3x2.5) -
VE-J6Y-MX Vicor Corporation DC DC CONVERTER 3.3V 50W Op voorraad4680 pcs 90% 1 - 15A 200V 3.3V - - - 3 kV - - VE-J6Y Bulk Through Hole VE-J00™ (75W) -55°C ~ 100°C 2.28' L x 2.40' W x 0.50' H (57.9mm x 70.0mm x 12.7mm) 400V Isolated Module OCP, SCP ITE (Commercial) Half Brick - 50 W
VE-JW4-CX Vicor Corporation DC DC CONVERTER 48V 75W Op voorraad146 pcs 90% 1 - 1.56A 18V 48V - - - 3 kV - - VE-JW4 Bulk Through Hole VE-J00™ (75W) -25°C ~ 100°C 2.28' L x 2.40' W x 0.50' H (57.9mm x 70.0mm x 12.7mm) 36V Isolated Module OCP, SCP ITE (Commercial) Half Brick - 75 W
VI-B6L-CU Vicor Corporation DC DC CONVERTER 28V 200W Op voorraad112 pcs 90% 1 - 7.14A 200V 28V - - - 3 kV - - VI-B6L Bulk Through Hole VI-200™ (200W) -25°C ~ 85°C 4.60" L x 2.40" W x 0.50" H (116.8mm x 61.0mm x 12.7mm) 400V Isolated Module OCP, OTP, OVP, SCP ITE (Commercial) Full Brick - 200 W
VE-2T2-MW Vicor Corporation DC DC CONVERTER 15V 100W Op voorraad5340 pcs 90% 1 - 6.67A 66V 15V - - - 3 kV - - VE-2T2 Bulk Through Hole VE-200™ (100W) -55°C ~ 85°C 4.60" L x 2.40" W x 0.50" H (116.8mm x 61.0mm x 12.7mm) 160V Isolated Module OCP, OTP, OVP, SCP ITE (Commercial) Full Brick - 100 W
SXE15-48S1V8J Artesyn Embedded Power DC DC CONVERTER 1.8V 15W Op voorraad3840 pcs 83% 1 - 6A 33V 1.8V - - - 1.5 kV - - - Tray Surface Mount SXE15 (15W) -40°C ~ 70°C 1.91' L x 1.15' W x 0.34' H (48.4mm x 29.2mm x 8.5mm) 75V Isolated Module Remote On/Off, OCP, OVP, UVLO ITE (Commercial) 12-SMD Module, 6 Leads - 15 W
SQM48T25012-NAB0 Bel Power Solutions DC DC CONVERTER 1.2V 30W Op voorraad4820 pcs 79% 1 Enable, Active Low 25A 36V 1.2V - - - 2 kV - - - Bulk Through Hole SemiQ™ SQM48 -40°C ~ 85°C 2.30' L x 0.90' W x 0.33' H (58.4mm x 22.8mm x 8.5mm) 75V Isolated Module Remote On/Off, OCP, OTP, OVP, UVLO ITE (Commercial) 8-DIP Module, 1/8 Brick - 30 W
VI-J6Z-IZ Vicor Corporation VI-J6Z-IZ 300V/2V 5A Op voorraad5470 pcs - - - - - - - - - - - - VI-J6Z Bulk - * - - - - - - - - -
PPD1R5-48-1212 TDK-Lambda Americas Inc DC DC CONVERTER +/-12V 1.44W Op voorraad4200 pcs - 2 - 60mA, 60mA 32V 12V -12V - - - - - - - Through Hole PP (1.5W) -20°C ~ 71°C (With Derating) 1.30" L x 0.83" W x 0.31" H (33.0mm x 21.0mm x 8.0mm) 63V Isolated Module OVP ITE (Commercial) 5-DIP Module - 1.44 W
VE-J30-EX Vicor Corporation DC DC CONVERTER 5V 75W Op voorraad4610 pcs 88% 1 - 15A 42V 5V - - - 3 kV - - VE-J30 Bulk Through Hole VE-J00™ (75W) -10°C ~ 100°C 2.28" L x 2.40" W x 0.50" H (57.9mm x 70.0mm x 12.7mm) 60V Isolated Module OCP, SCP ITE (Commercial) Half Brick - 75 W
CCP-2403SF TDK-Lambda Americas Inc DC DC CONVERTER 3.3V 7.59W Op voorraad4850 pcs 80% 1 - 2.3A 18V 3.3V - - - 500 V - - - Bulk Through Hole CCP (10W) -20°C ~ 70°C (With Derating) 1.79" L x 1.38" W x 0.33" H (45.5mm x 35.1mm x 8.4mm) 36V Isolated Module OCP ITE (Commercial) 8-DIP Module - 7.59 W
VE-26Z-CX Vicor Corporation DC DC CONVERTER 2V 30W Op voorraad3700 pcs 90% 1 - 30A 200V 2V - - - 3 kV - - VE-26Z Bulk Through Hole VE-200™ (75W) -25°C ~ 85°C 4.60' L x 2.40' W x 0.50' H (116.8mm x 61.0mm x 12.7mm) 400V Isolated Module OCP, OTP, OVP, SCP ITE (Commercial) Full Brick - 30 W
SIL60C2-00SADJ-VDJ Artesyn Embedded Power DC DC CONVERTER 0.8-4V 240W Op voorraad1043 pcs 89% 1 - 60A 4.5V 0.8 ~ 4V - - - - - - SIL60C2 Tray Through Hole SIL60C2 (240W) 0°C ~ 70°C 1.98" L x 0.55" W x 0.80" H (50.3mm x 13.9mm x 20.3mm) 13.8V Non-Isolated PoL Module Remote On/Off, OCP, OVP, SCP ITE (Commercial) 38-SIP Formed Leads - 240 W
MI-J60-MA Vicor Corporation DC DC CONVERTER 5V 10W Op voorraad47 pcs 90% 1 - 2A 125V 5V - - - 3 kV - - MI-J60 Bulk Through Hole MI-J00™ (10W) -55°C ~ 85°C 2.40' L x 2.28' W x 0.50' H (61.0mm x 57.9mm x 12.7mm) 400V Isolated Module Remote On/Off, OCP, OTP, OVP ITE (Commercial) 9-DIP Module - 10 W
VI-264-VU Vicor Corporation VI-264-VU 300V/48V 200W Op voorraad78 pcs - - - - - - - - - - - - VI-264 Bulk - * - - - - - - - - -
VE-J21-MY Vicor Corporation DC DC CONVERTER 12V 50W Op voorraad3880 pcs 90% 1 - 4.17A 21V 12V - - - 3 kV - - VE-J21 Bulk Through Hole VE-J00™ (50W) -55°C ~ 100°C 2.28' L x 2.40' W x 0.50' H (57.9mm x 70.0mm x 12.7mm) 56V Isolated Module OCP, SCP ITE (Commercial) Half Brick - 50 W
PCD3-5-1212 TDK-Lambda Americas Inc DC DC CONVERTER +/-12V 3W Op voorraad3900 pcs - 2 - 125mA, 125mA 4.5V 12V -12V - - - - - - - Through Hole PC -20°C ~ 70°C (With Derating) 1.09" L x 0.78" W x 0.33" H (27.8mm x 19.8mm x 8.5mm) 9V Isolated Module OCP ITE (Commercial) 6-DIP Module - 3 W
KNW015A0F41-88SRZ ABB Power Electronics Inc. DC DC CONVERTER 3.3V 50W Op voorraad4270 pcs 92% 1 Enable, Active Low 15A 36V 3.3V - - - 2.25 kV - - - Tape & Reel (TR) Through Hole KNW015A0F -40°C ~ 85°C 1.30" L x 0.90" W x 0.40" H (33.0mm x 22.9mm x 10.2mm) 75V Isolated Module Remote On/Off, OCP, OTP, OVP, UVLO ITE (Commercial) 8-DIP Module - 50 W
VI-J51-09 Vicor Corporation VI-J51-09 150V/12V 25W Op voorraad4280 pcs - - - - - - - - - - - - VI-J51 Bulk - * - - - - - - - - -
VE-JW2-MX Vicor Corporation DC DC CONVERTER 15V 75W Op voorraad37 pcs 90% 1 - 5A 18V 15V - - - 3 kV - - VE-JW2 Bulk Through Hole VE-J00™ (75W) -55°C ~ 100°C 2.28" L x 2.40" W x 0.50" H (57.9mm x 70.0mm x 12.7mm) 36V Isolated Module OCP, SCP ITE (Commercial) Half Brick - 75 W
VE-JT3-CX Vicor Corporation DC DC CONVERTER 24V 75W Op voorraad128 pcs 90% 1 - 3.13A 66V 24V - - - 3 kV - - VE-JT3 Bulk Through Hole VE-J00™ (75W) -25°C ~ 100°C 2.28' L x 2.40' W x 0.50' H (57.9mm x 70.0mm x 12.7mm) 160V Isolated Module OCP, SCP ITE (Commercial) Half Brick - 75 W
VI-BWZ-CV Vicor Corporation DC DC CONVERTER 2V 60W Op voorraad5300 pcs 90% 1 - 30A 18V 2V - - - 3 kV - - VI-BWZ Bulk Through Hole VI-200™ (150W) -25°C ~ 85°C 4.60' L x 2.40' W x 0.50' H (116.8mm x 61.0mm x 12.7mm) 36V Isolated Module OCP, OTP, OVP, SCP ITE (Commercial) Full Brick - 60 W
FPMR12TR7510PE FDK America, Inc., a member of Fujitsu Group DC DC CONVERTER Op voorraad5470 pcs - - - - - - - - - - - - - Bulk - - - - - - - - - - -
VI-912033B Vicor Corporation T 150/400/233 26.4V/ 11.7A Op voorraad75 pcs - - - - - - - - - - - - - Bulk - * - - - - - - - - -
VE-J53-MY Vicor Corporation DC DC CONVERTER 24V 50W Op voorraad5330 pcs 90% 1 - 2.08A 100V 24V - - - 3 kV - - VE-J53 Bulk Through Hole VE-J00™ (50W) -55°C ~ 100°C 2.28' L x 2.40' W x 0.50' H (57.9mm x 70.0mm x 12.7mm) 200V Isolated Module OCP, SCP ITE (Commercial) Half Brick - 50 W
PSS6-24-5 TDK-Lambda Americas Inc DC DC CONVERTER 5V 6W Op voorraad4080 pcs 84% 1 - 1.2A 18V 5V - - - - - - - Bulk Through Hole PSS (6W) -40°C ~ 85°C (With Derating) 1.12" L x 0.80" W x 0.31" H (28.4mm x 20.3mm x 8.0mm) 36V Isolated Module Remote On/Off, OCP ITE (Commercial) 6-DIP Module 6-DIP Module 6 W
QRW025A0F41-H ABB Power Electronics Inc. DC DC CONVERTER 3.3V 83W Op voorraad3700 pcs 91% 1 Enable, Active Low 25A 36V 3.3V - - - 1.5 kV - - - Tray Through Hole QRW025 -40°C ~ 85°C 2.29' L x 1.46' W x 0.37' H (58.2mm x 37.1mm x 9.4mm) 75V Isolated Module Remote On/Off, OCP, OTP, OVP ITE (Commercial) 10-DIP Module, 1/4 Brick - 83 W
VE-J23-EX Vicor Corporation DC DC CONVERTER 24V 75W Op voorraad146 pcs 88% 1 - 3.13A 21V 24V - - - 3 kV - - VE-J23 Bulk Through Hole VE-J00™ (75W) -10°C ~ 100°C 2.28' L x 2.40' W x 0.50' H (57.9mm x 70.0mm x 12.7mm) 56V Isolated Module OCP, SCP ITE (Commercial) Half Brick - 75 W
RFB350-48S12-R5TY Artesyn Embedded Power DC DC CONVERTER 12V 350W Op voorraad4220 pcs 88% 1 Enable, Active Low 29.2A 36V 12V - - - 1.5 kV - - - Tray Through Hole RFB350 (350W) -40°C ~ 100°C 2.39" L x 2.27" W x 0.50" H (60.7mm x 57.7mm x 12.7mm) 75V Isolated Module Remote On/Off, OCP, OTP, OVP, SCP, UVLO ITE (Commercial) 9-DIP Module, 1/2 Brick - 350 W
VE-251-CU Vicor Corporation DC DC CONVERTER 12V 200W Op voorraad70 pcs 90% 1 - 16.67A 100V 12V - - - 3 kV - - VE-251 Bulk Through Hole VE-200™ (200W) -25°C ~ 85°C 4.60" L x 2.40" W x 0.50" H (116.8mm x 61.0mm x 12.7mm) 200V Isolated Module OCP, OTP, OVP, SCP ITE (Commercial) Full Brick - 200 W
CHS4002424-B Cosel USA, Inc. DC DC CONVERTER 24V 348W Op voorraad304 pcs 94% 1 Enable, Active Low 14.5A 18V 24V - - - 2.25 kV CE, cURus, TUV - CHS4002424 Box Through Hole CHS (400W) -40°C ~ 85°C (With Derating) 2.32" L x 1.47" W x 0.50" H (58.9mm x 37.3mm x 12.7mm) 36V Isolated Module Adjustable Output, Baseplate, Remote Sense ITE (Commercial) Quarter Brick Quarter Brick 348 W
MI-J20-MA Vicor Corporation DC DC CONVERTER 5V 10W Op voorraad62 pcs 90% 1 - 2A 18V 5V - - - 3 kV - - MI-J20 Bulk Through Hole MI-J00™ (10W) -55°C ~ 85°C 2.40' L x 2.28' W x 0.50' H (61.0mm x 57.9mm x 12.7mm) 50V Isolated Module Remote On/Off, OCP, OTP, OVP ITE (Commercial) 9-DIP Module - 10 W
PTH05060YAZ Artesyn Embedded Power DC DC CONVERTER 0.55-1.8V 18W Op voorraad3960 pcs 86% 1 - 10A 4.5V 0.55 ~ 1.8V - - - - - - - Tray Surface Mount PTHxx060Y (18W) -40°C ~ 85°C 1.00" L x 0.62" W x 0.35" H (25.3mm x 15.8mm x 9.0mm) 5.5V Non-Isolated PoL Module Remote On/Off, OCP, UVLO ITE (Commercial) 10-SMD Module, 7 Leads - 18 W
CXA10-48D12J Artesyn Embedded Power DC DC CONVERTER +/-12V 10W Op voorraad824 pcs 83% 2 - 410mA, 410mA 18V 12V -12V - - 1.5 kV - - CXA10 Tray Through Hole CXA10 (10W) -40°C ~ 70°C 2.00" L x 1.00" W x 0.39" H (50.8mm x 25.4mm x 10.0mm) 75V Isolated Module OVP, SCP, UVLO ITE (Commercial) 6-DIP Module - 10 W
PP1R5-24-12 TDK-Lambda Americas Inc DC DC CONVERTER 12V 1.44W Op voorraad3760 pcs - 1 - 120mA 18V 12V - - - - - - - - Through Hole PP (1.5W) -20°C ~ 71°C (With Derating) 1.30" L x 0.83" W x 0.31" H (33.0mm x 21.0mm x 8.0mm) 36V Isolated Module Remote On/Off, OVP ITE (Commercial) 4-DIP Module - 1.44 W
RBQ-31251-CIS Murata Power Solutions Inc. DC DC CONVERTER Op voorraad4550 pcs - - - - - - - - - - - - RBQ-31 Tray - - - - - - - - - - -
VI-B63-CX Vicor Corporation DC DC CONVERTER 24V 75W Op voorraad3730 pcs 90% 1 - 3.13A 200V 24V - - - 3 kV - - VI-B63 Bulk Through Hole VI-200™ (75W) -25°C ~ 85°C 4.60' L x 2.40' W x 0.50' H (116.8mm x 61.0mm x 12.7mm) 400V Isolated Module OCP, OTP, OVP, SCP ITE (Commercial) Full Brick - 75 W
MW010A1 ABB Power Electronics Inc. DC DC CONVERTER 5V 10W Op voorraad3880 pcs 80% 1 Enable, Active Low 2A 36V 5V - - - 500 V - - - Bulk Through Hole MW010 (10W) -40°C ~ 85°C 2.00" L x 1.60" W x 0.50" H (50.8mm x 40.6mm x 12.7mm) 75V Isolated Module Remote On/Off, OCP, OVP ITE (Commercial) 4-DIP Module - 10 W
VE-J3Z-CZ Vicor Corporation DC DC CONVERTER 2V 10W Op voorraad4560 pcs 90% 1 - 5A 42V 2V - - - 3 kV - - VE-J3Z Bulk Through Hole VE-J00™ (25W) -25°C ~ 100°C 2.28' L x 2.40' W x 0.50' H (57.9mm x 70.0mm x 12.7mm) 60V Isolated Module OCP, SCP ITE (Commercial) Half Brick - 10 W
VI-200-27 Vicor Corporation VI-200-27 12V/5V 75W Op voorraad123 pcs - - - - - - - - - - - - VI-200 Bulk - * - - - - - - - - -
VE-244-IV Vicor Corporation DC DC CONVERTER 48V 150W Op voorraad4250 pcs 90% 1 - 3.13A 55V 48V - - - 3 kV - - VE-244 Bulk Through Hole VE-200™ (150W) -40°C ~ 85°C 4.60' L x 2.40' W x 0.50' H (116.8mm x 61.0mm x 12.7mm) 100V Isolated Module OCP, OTP, OVP, SCP ITE (Commercial) Full Brick - 150 W
HBS050ZG-A Bel Power Solutions DC DC CONVERTER 5V 50W Op voorraad5250 pcs 82% 1 Enable, Active High 10A 34V 5V - - - 1.5 kV - - - Bulk Through Hole HBS (50W) -40°C ~ 100°C 2.40" L x 2.28" W x 0.50" H (61.0mm x 57.9mm x 12.7mm) 75V Isolated Module Remote On/Off, OCP, OTP, OVP, SCP ITE (Commercial) 9-DIP Module - 50 W
VE-2N4-EY Vicor Corporation DC DC CONVERTER 48V 50W Op voorraad4200 pcs 88% 1 - 1.04A 36V 48V - - - 3 kV - - VE-2N4 Bulk Through Hole VE-200™ (50W) -10°C ~ 85°C 4.60' L x 2.40' W x 0.50' H (116.8mm x 61.0mm x 12.7mm) 76V Isolated Module OCP, OTP, OVP, SCP ITE (Commercial) Full Brick - 50 W
VE-273-CY Vicor Corporation DC DC CONVERTER 24V 50W Op voorraad3870 pcs 90% 1 - 2.08A 100V 24V - - - 3 kV - - VE-273 Bulk Through Hole VE-200™ (50W) -25°C ~ 85°C 4.60" L x 2.40" W x 0.50" H (116.8mm x 61.0mm x 12.7mm) 375V Isolated Module OCP, OTP, OVP, SCP ITE (Commercial) Full Brick - 50 W
1...184185186187188189190...233
0 RFQ
Winkelmand (0 Items)
Het is leeg.
Vergelijk lijst (0 Items)
Het is leeg.
Feedback

Uw feedback is belangrijk!Bij Allelco waarderen we de gebruikerservaring en streven we ernaar deze constant te verbeteren.
Deel uw opmerkingen met ons via ons feedbackformulier en we zullen onmiddellijk reageren.
Bedankt voor het kiezen van Allelco.

Onderwerp
E-mail
Comments
Captcha
Sleep of klik om het bestand te uploaden
Upload bestand
Typen: .xls, .xlsx, .doc, .Docx, .jpg, .png en .pdf.
MAX -bestandsgrootte: 10 MB