Contact Us:00852-30501886 Email:sales@allicdata.com
Sitemap How to buy Login / Register
USD
USA EN
Cart(0)
Products Manufacturers Authorized Agent Send RFQ Blog（news） About us
Home> Products>

Search Result:thyristor in parallel

 --674 Item(s) In Category:Evaluation Boards - Analog to Digital Converters (ADCs)

Related Categories

Integrated Circuits (ICs)
Memory
Data Acquisition - Analog to D...
Data Acquisition - Digital to ...
PMIC - Motor Drivers, Controll...
Logic - Shift Registers
Clock/Timing - Real Time Clock...
Data Acquisition - ADCs/DACs -...
Interface - Controllers
PMIC - Power Distribution Swit...
Interface - Telecom
Interface - Specialized
Interface - I/O Expanders
PMIC - Display Drivers
Embedded - Microprocessors
Data Acquisition - Digital Pot...
Interface - Serializers, Deser...
Embedded - Microcontrollers - ...
Embedded - DSP (Digital Signal...
Data Acquisition - Touch Scree...
Interface - Sensor and Detecto...
PMIC - Thermal Management
Interface - Modules
PMIC - OR Controllers, Ideal D...
Embedded - Microcontrollers
PMIC - Power Over Ethernet (Po...
Transformers
Power Transformers
Switching Converter, SMPS Tran...
Inductors, Coils, Chokes
Arrays, Signal Transformers
Fixed Inductors
Optoelectronics
Display Modules - LCD, OLED, G...
Display Modules - LCD, OLED Ch...
Display Modules - Vacuum Fluor...
Display Modules - LED Dot Matr...
Fiber Optics - Transceiver Mod...
Accessories
Discrete Semiconductor Products
Thyristors - SCRs
Thyristors - SCRs - Modules
Thyristors - DIACs, SIDACs
Transistors - Programmable Uni...
Thyristors - TRIACs
Diodes - RF
Development Boards, Kits, Progra...
Evaluation Boards - Analog to ...
Evaluation Boards - Digital to...
Evaluation and Demonstration B...
Accessories
Evaluation Boards - Sensors
Programmers, Emulators, and De...
Evaluation Boards - Expansion ...
Software, Services
Circuit Protection
TVS - Thyristors
TVS - Mixed Technology
Accessories
Electrical, Specialty Fuses
Resistors
Resistor Networks, Arrays
Connectors, Interconnects
Terminal Blocks - Wire to Boar...
Terminals - Wire Splice Connec...
Terminal Blocks - Panel Mount
Terminal Blocks - Headers, Plu...
Backplane Connectors - Special...
Between Series Adapters
D-Shaped Connectors - Centroni...
Cables, Wires - Management
Cable Ties and Cable Lacing
Accessories
Cable Supports and Fasteners
Switches
Selector Switches
Snap Action, Limit Switches
Cable Assemblies
Between Series Adapter Cables
D-Sub Cables
Fiber Optic Cables
Smart Cables
Computers, Office - Components, ...
Modems
Adapters, Converters
Printers, Label Makers
Tools
Punches
Accessories
Uncategorized
Miscellaneous
RF/IF and RFID
RF Accessories
RF Amplifiers
RF Transceiver Modules
RF Misc ICs and Modules
RF Receivers
RF Transmitters
Industrial Controls
Protection Relays & System...
Machine Vision - Accessories
Machine Vision - Control/Proce...
Accessories
Hardware, Fasteners, Accessories
Hole Plugs
Relays
Accessories
Sensors, Transducers
Accessories
Networking Solutions
Miscellaneous
Test and Measurement
Equipment - Power Supplies (Te...
Kits
Discrete Assortment Kits
Line Protection, Distribution, B...
Accessories
Power Distribution, Surge Prot...
Power Supplies - External/Intern...
Accessories
Audio Products
Alarms, Buzzers, and Sirens
Boxes, Enclosures, Racks
Card Rack Accessories
Embedded Computers
Accessories
Interface Boards
Maker/DIY, Educational
Robotics Kits
Photo Allicdata Part# Mft.Part# Company Spec. QTY. Pricing(USD) PDF
TLC5540EVM 296-10337-ND TLC5540EVM Texas Instruments
View more  Part Status: Active
 Number of A/D Converters: 1
 Number of Bits: 8
 Sampling Rate (Per Second): 40M
 Data Interface: Parallel
 Input Range: 0 ~ 5 V
 Power (Typ) @ Conditions: 85mW @ 5 V
 Utilized IC / Part: TLC5540
 Supplied Contents: Board(s)
5
Order

1+:

$32.0544

 296-10337-ND Datasheet
MAX19516EVKIT+ MAX19516EVKIT+-
ND		 MAX19516EVKIT+ Maxim Integrated
View more  Part Status: Active
 Number of A/D Converters: 2
 Number of Bits: 10
 Sampling Rate (Per Second): 100M
 Data Interface: Serial, Parallel
 Input Range: 0.4 ~ 1.4 V
 Power (Typ) @ Conditions: 57mW @ 100MSPS, 1.8 V
 Utilized IC / Part: MAX19516
 Supplied Contents: Board(s)
1000
Order

1+:

$0

 MAX19516EVKIT+-ND Datasheet
ADS5482EVM 296-45595-ND ADS5482EVM Texas Instruments
View more  Part Status: Active
 Number of A/D Converters: 1
 Number of Bits: 16
 Sampling Rate (Per Second): 105M
 Data Interface: Parallel
 Input Range: 3 Vpp
 Power (Typ) @ Conditions: 2.15W @ 105MSPS
 Utilized IC / Part: ADS5482
 Supplied Contents: Board(s)
2
Order

1+:

$195.602

 296-45595-ND Datasheet
ADS8364EVM ADS8364EVM-ND ADS8364EVM Texas Instruments
View more  Part Status: Obsolete
 Number of A/D Converters: 6
 Number of Bits: 16
 Sampling Rate (Per Second): 250k
 Data Interface: Parallel
 Input Range: 0 ~ 5 V
 Power (Typ) @ Conditions: 413.5mW @ 250kSPS
 Utilized IC / Part: ADS8364
 Supplied Contents: Board(s)
1000
Order

1+:

$0

 ADS8364EVM-ND Datasheet
ADS8422EVM 296-23030-ND ADS8422EVM Texas Instruments
View more  Part Status: Obsolete
 Number of A/D Converters: 1
 Number of Bits: 16
 Sampling Rate (Per Second): 4M
 Data Interface: Parallel
 Input Range: 0 ~ 4 V
 Power (Typ) @ Conditions: 155mW @ 4MSPS
 Utilized IC / Part: ADS8422-ADC
 Supplied Contents: Board(s)
1000
Order

1+:

$0

 296-23030-ND Datasheet
MAX1193EVKIT MAX1193EVKIT-ND MAX1193EVKIT Maxim Integrated
View more  Part Status: Active
 Number of A/D Converters: 2
 Number of Bits: 8
 Sampling Rate (Per Second): 45M
 Data Interface: Parallel
 Input Range: 512 mV
 Utilized IC / Part: MAX1191, MAX1192, MAX1193
 Supplied Contents: Board(s)
1000
Order

1+:

$0

 MAX1193EVKIT-ND Datasheet
ADS5410EVM 296-30657-ND ADS5410EVM Texas Instruments
View more  Series: CommsADC
 Part Status: Obsolete
 Number of A/D Converters: 1
 Number of Bits: 12
 Sampling Rate (Per Second): 80M
 Data Interface: Parallel
 Input Range: 2 Vpp
 Power (Typ) @ Conditions: 360mW @ 80MSPS
 Utilized IC / Part: ADS5410
 Supplied Contents: Board(s)
1000
Order

1+:

$0

 296-30657-ND Datasheet
IDTADC1206S040-DB IDTADC1206S040-
DB-ND		 IDTADC1206S040-
DB		 IDT, Integrated Device Technology Inc
View more  Part Status: Obsolete
 Number of A/D Converters: 1
 Number of Bits: 12
 Sampling Rate (Per Second): 40M
 Data Interface: Parallel
 Utilized IC / Part: ADC1206S040
 Supplied Contents: Board(s)
1000
Order

1+:

$0

 IDTADC1206S040-DB-ND Datasheet
AD10242/PCB AD10242/PCB-ND AD10242/PCB Analog Devices Inc.
View more  Part Status: Active
 Number of A/D Converters: 2
 Number of Bits: 12
 Sampling Rate (Per Second): 40M
 Data Interface: Parallel
 Input Range: 2 V
 Power (Typ) @ Conditions: 1.75W @ 40MSPS
 Utilized IC / Part: AD10242
 Supplied Contents: Board(s)
 Base Part Number: AD10242
1000
Order

1+:

$0

 AD10242/PCB-ND Datasheet
ADS5545EVM 296-19452-ND ADS5545EVM Texas Instruments
View more  Part Status: Obsolete
 Number of A/D Converters: 1
 Number of Bits: 14
 Sampling Rate (Per Second): 170M
 Data Interface: Serial, Parallel
 Input Range: 1 ~ 2 Vpp
 Power (Typ) @ Conditions: 1.1W @ 170MSPS
 Utilized IC / Part: ADS5545
 Supplied Contents: Board(s)
1000
Order

1+:

$0

 296-19452-ND Datasheet
ADS4125EVM 296-30645-ND ADS4125EVM Texas Instruments
View more  Part Status: Active
 Number of A/D Converters: 1
 Number of Bits: 12
 Sampling Rate (Per Second): 125M
 Data Interface: CMOS, LVDS, Serial, Parallel
 Input Range: 2 Vpp
 Utilized IC / Part: ADS4125
 Supplied Contents: Board(s)
2
Order

1+:

$195.602

 296-30645-ND Datasheet
DC2365A-F DC2365A-F-ND DC2365A-F Linear Technology/Analog Devices
View more  Part Status: Active
 Number of A/D Converters: 4
 Number of Bits: 16
 Sampling Rate (Per Second): 350k
 Data Interface: Parallel
 Input Range: 10.24 V
 Utilized IC / Part: LTC2357-16
 Supplied Contents: Board(s)
 Base Part Number: LTC2357
3
Order

1+:

$96.39

 DC2365A-F-ND Datasheet
THS1403EVM 296-10015-ND THS1403EVM Texas Instruments
View more  Part Status: Obsolete
 Number of A/D Converters: 1
 Number of Bits: 14
 Sampling Rate (Per Second): 3M
 Data Interface: Parallel
 Input Range: 0 ~ 3.6 V
 Power (Typ) @ Conditions: 270mW @ 3MSPS
 Utilized IC / Part: THS1403
 Supplied Contents: Board(s)
1000
Order

1+:

$0

 296-10015-ND Datasheet
AD676-EB AD676-EB-ND AD676-EB Analog Devices Inc.
View more  Part Status: Obsolete
 Number of A/D Converters: 1
 Number of Bits: 16
 Sampling Rate (Per Second): 100k
 Data Interface: Parallel
 Input Range: VREF
 Power (Typ) @ Conditions: 360mW @ 100kSPS
 Utilized IC / Part: AD676
 Supplied Contents: Board(s)
 Base Part Number: AD676
1000
Order

1+:

$0

 AD676-EB-ND Datasheet
MAX12557EVKIT MAX12557EVKIT-N
D		 MAX12557EVKIT Maxim Integrated
View more  Part Status: Active
 Number of A/D Converters: 2
 Number of Bits: 14
 Sampling Rate (Per Second): 65M
 Data Interface: Parallel
 Input Range: 1.024 V
 Power (Typ) @ Conditions: 637mW @ 65MSPS
 Utilized IC / Part: MAX12557
 Supplied Contents: Board(s)
1000
Order

1+:

$0

 MAX12557EVKIT-ND Datasheet
MAX125EVKIT MAX125EVKIT-ND MAX125EVKIT Maxim Integrated
View more  Part Status: Active
 Number of A/D Converters: 4
 Number of Bits: 14
 Sampling Rate (Per Second): 250k
 Data Interface: Parallel
 Input Range: 5 V
 Power (Typ) @ Conditions: 165mW @ 250kSPS
 Utilized IC / Part: MAX125
 Supplied Contents: Board(s)
995
Order

1+:

$47.1366

 MAX125EVKIT-ND Datasheet
EVAL-AD976ACB EVAL-AD976ACB-N
D		 EVAL-AD976ACB Analog Devices Inc.
View more  Part Status: Obsolete
 Number of A/D Converters: 1
 Number of Bits: 16
 Sampling Rate (Per Second): 200k
 Data Interface: Parallel
 Input Range: 10 V
 Power (Typ) @ Conditions: 100mW @ 200kSPS
 Utilized IC / Part: AD976A
 Supplied Contents: Board(s)
 Base Part Number: AD976
1000
Order

1+:

$0

 EVAL-AD976ACB-ND Datasheet
ADS42JB69SEK 296-36474-ND ADS42JB69SEK Texas Instruments
View more  Part Status: Obsolete
 Number of A/D Converters: 2
 Number of Bits: 16
 Sampling Rate (Per Second): 250M
 Data Interface: JESD204B, Parallel, Serial, SPI
 Input Range: 2 Vpp
 Utilized IC / Part: ADS42JB69
 Supplied Contents: Board(s)
2
Order

1+:

$0.63

 296-36474-ND Datasheet
THS10082EVM 296-10001-ND THS10082EVM Texas Instruments
View more  Part Status: Obsolete
 Number of A/D Converters: 1
 Number of Bits: 10
 Sampling Rate (Per Second): 8M
 Data Interface: Parallel
 Power (Typ) @ Conditions: 186mW @ 5 V AVdd, 3.3 V DVdd
 Utilized IC / Part: THS10082
 Supplied Contents: Board(s)
1000
Order

1+:

$0

 296-10001-ND Datasheet
MAX197EVC32-DIP MAX197EVC32-DIP
-ND		 MAX197EVC32-DIP Maxim Integrated
View more  Part Status: Active
 Number of A/D Converters: 1
 Number of Bits: 12
 Sampling Rate (Per Second): 100k
 Data Interface: Parallel
 Input Range: 10 V
 Utilized IC / Part: MAX197, MAX199
 Supplied Contents: Board(s)
1000
Order

1+:

$0

 MAX197EVC32-DIP-ND Datasheet
HI5746EVAL1 HI5746EVAL1-ND HI5746EVAL1 Renesas Electronics America Inc.
View more  Part Status: Obsolete
 Number of A/D Converters: 1
 Number of Bits: 10
 Sampling Rate (Per Second): 40M
 Data Interface: Parallel
 Input Range: 1 Vpp
 Power (Typ) @ Conditions: 225mW @ 40MSPS
 Utilized IC / Part: HI5746
 Supplied Contents: Board(s)
1000
Order

1+:

$0

 HI5746EVAL1-ND Datasheet
ADS62P45EVM 296-30688-ND ADS62P45EVM Texas Instruments
View more  Part Status: Obsolete
 Number of A/D Converters: 2
 Number of Bits: 14
 Sampling Rate (Per Second): 125M
 Data Interface: Serial, Parallel
 Input Range: 2 Vpp
 Power (Typ) @ Conditions: 799mW @ 125MSPS
 Utilized IC / Part: ADS62P45
 Supplied Contents: Board(s)
1000
Order

1+:

$0

 296-30688-ND Datasheet
DC996B-A DC996B-A-ND DC996B-A Linear Technology/Analog Devices
View more  Part Status: Active
 Number of A/D Converters: 1
 Number of Bits: 16
 Sampling Rate (Per Second): 130M
 Data Interface: Parallel
 Input Range: 2.25 Vpp
 Power (Typ) @ Conditions: 1.498W @ 130MSPS
 Utilized IC / Part: LTC2208
 Supplied Contents: Board(s)
 Base Part Number: LTC2208
3
Order

1+:

$128.52

 DC996B-A-ND Datasheet
MAX116XXSPIMB# MAX116XXSPIMB#-
ND		 MAX116XXSPIMB# Maxim Integrated
View more  Part Status: Active
 Number of A/D Converters: 1
 Number of Bits: 12
 Data Interface: Parallel
 Input Range: 2.5 V
 Utilized IC / Part: MAX116
 Supplied Contents: Board(s)
1000
Order

1+:

$114.062

 MAX116XXSPIMB#-ND Datasheet
MAX19507EVKIT+ MAX19507EVKIT+-
ND		 MAX19507EVKIT+ Maxim Integrated
View more  Part Status: Active
 Number of A/D Converters: 2
 Number of Bits: 8
 Sampling Rate (Per Second): 130M
 Data Interface: Serial, Parallel
 Input Range: 0.4 ~ 1.4 V
 Power (Typ) @ Conditions: 74mW @ 130MSPS, 1.8 V
 Utilized IC / Part: MAX19507
 Supplied Contents: Board(s)
1000
Order

1+:

$0

 MAX19507EVKIT+-ND Datasheet
ADS4246EVM 296-30651-ND ADS4246EVM Texas Instruments
View more  Part Status: Active
 Number of A/D Converters: 2
 Number of Bits: 14
 Sampling Rate (Per Second): 160M
 Data Interface: CMOS, LVDS, Serial, Parallel
 Input Range: 2 Vpp
 Utilized IC / Part: ADS4246
 Supplied Contents: Board(s)
1
Order

1+:

$195.602

 296-30651-ND Datasheet
ADC1175-50EVAL ADC1175-50EVAL-
ND		 ADC1175-50EVAL Texas Instruments
View more  Part Status: Obsolete
 Number of A/D Converters: 1
 Number of Bits: 8
 Sampling Rate (Per Second): 50M
 Data Interface: Parallel
 Utilized IC / Part: ADC1175-50
 Supplied Contents: Board(s)
1000
Order

1+:

$0

 ADC1175-50EVAL-ND Datasheet
ADC14C080EB/NOPB ADC14C080EB/NOP
B-ND		 ADC14C080EB/NOP
B		 Texas Instruments
View more  Part Status: Obsolete
 Number of A/D Converters: 1
 Number of Bits: 14
 Sampling Rate (Per Second): 80M
 Data Interface: Parallel
 Input Range: 2 Vpp
 Power (Typ) @ Conditions: 300mW @ 80 MSPS
 Utilized IC / Part: ADC14C080
 Supplied Contents: Board(s)
1000
Order

1+:

$0

 ADC14C080EB/NOPB-ND Datasheet
ADS5463EVM-CVAL ADS5463EVM-CVAL
-ND		 ADS5463EVM-CVAL Texas Instruments
View more  Part Status: Active
 Number of A/D Converters: 1
 Number of Bits: 12
 Sampling Rate (Per Second): 500M
 Data Interface: LVDS - Parallel
 Input Range: 2.2 Vpp
 Power (Typ) @ Conditions: 2.425W @ 500MSPS
 Utilized IC / Part: ADS5463-SP
 Supplied Contents: Board(s)
1000
Order

1+:

$0

 ADS5463EVM-CVAL-ND Datasheet
ADC12DL080EVAL ADC12DL080EVAL-
ND		 ADC12DL080EVAL Texas Instruments
View more  Part Status: Obsolete
 Number of A/D Converters: 2
 Number of Bits: 12
 Sampling Rate (Per Second): 80M
 Data Interface: Parallel
 Input Range: 2 Vpp
 Power (Typ) @ Conditions: 447mW @ 80MSPS
 Utilized IC / Part: ADC12DL080
 Supplied Contents: Board(s)
1000
Order

1+:

$0

 ADC12DL080EVAL-ND Datasheet
DC1098A-A DC1098A-A-ND DC1098A-A Linear Technology/Analog Devices
View more  Part Status: Active
 Number of A/D Converters: 2
 Number of Bits: 10
 Sampling Rate (Per Second): 125M
 Data Interface: Parallel
 Input Range: 2 Vpp
 Power (Typ) @ Conditions: 790mW @ 125MSPS
 Utilized IC / Part: LTC2281
 Supplied Contents: Board(s)
 Base Part Number: LTC2281
4
Order

1+:

$128.52

 DC1098A-A-ND Datasheet
ADS5220EVM ADS5220EVM-ND ADS5220EVM Texas Instruments
View more  Part Status: Obsolete
 Number of A/D Converters: 1
 Number of Bits: 12
 Sampling Rate (Per Second): 40M
 Data Interface: Parallel
 Input Range: 2 Vpp
 Utilized IC / Part: ADS5220
 Supplied Contents: Board(s)
1000
Order

1+:

$0

 ADS5220EVM-ND Datasheet
ADS6243EVM ADS6243EVM-ND ADS6243EVM Texas Instruments
View more  Part Status: Obsolete
 Number of A/D Converters: 2
 Number of Bits: 14
 Sampling Rate (Per Second): 80M
 Data Interface: Serial, Parallel
 Input Range: 2 Vpp
 Power (Typ) @ Conditions: 350mW @ 80MSPS
 Utilized IC / Part: ADS6243
 Supplied Contents: Board(s)
1000
Order

1+:

$0

 ADS6243EVM-ND Datasheet
ADS8323EVM 296-19918-ND ADS8323EVM Texas Instruments
View more  Series: microPOWER
 Part Status: Active
 Number of A/D Converters: 1
 Number of Bits: 16
 Sampling Rate (Per Second): 500k
 Data Interface: Parallel
 Input Range: 0 ~ 5 V
 Power (Typ) @ Conditions: 85mW @ 500kSPS
 Utilized IC / Part: ADS8323
 Supplied Contents: Board(s)
3
Order

1+:

$64.764

 296-19918-ND Datasheet
DC854D-F DC854D-F-ND DC854D-F Linear Technology/Analog Devices
View more  Part Status: Active
 Number of A/D Converters: 1
 Number of Bits: 16
 Sampling Rate (Per Second): 105M
 Data Interface: Parallel
 Input Range: 2.25 Vpp
 Power (Typ) @ Conditions: 1.45W @ 105MSPS
 Utilized IC / Part: LTC2217
 Supplied Contents: Board(s)
 Base Part Number: LTC2217
4
Order

1+:

$128.52

 DC854D-F-ND Datasheet
ADS6424EVM 296-30691-ND ADS6424EVM Texas Instruments
View more  Part Status: Obsolete
 Number of A/D Converters: 4
 Number of Bits: 12
 Sampling Rate (Per Second): 105M
 Data Interface: Serial, Parallel
 Input Range: 2 Vpp
 Power (Typ) @ Conditions: 340mw @ 105MSPS
 Utilized IC / Part: ADS6424
 Supplied Contents: Board(s)
1
Order

1+:

$189.85

 296-30691-ND Datasheet
DEM-ADS807E 296-18423-ND DEM-ADS807E Texas Instruments
View more  Part Status: Obsolete
 Number of A/D Converters: 1
 Number of Bits: 12
 Sampling Rate (Per Second): 53M
 Data Interface: Parallel
 Input Range: 2 ~ 3 Vpp
 Power (Typ) @ Conditions: 335mW @ 53MSPS
 Utilized IC / Part: ADS807E
 Supplied Contents: Board(s)
1000
Order

1+:

$0

 296-18423-ND Datasheet
ADC12DC080LFEB/NOPB ADC12DC080LFEB/
NOPB-ND		 ADC12DC080LFEB/
NOPB		 Texas Instruments
View more  Part Status: Obsolete
 Number of A/D Converters: 2
 Number of Bits: 12
 Sampling Rate (Per Second): 80M
 Data Interface: Parallel
 Input Range: 2 Vpp
 Power (Typ) @ Conditions: 600mW @ 80MSPS
 Utilized IC / Part: ADC12DC080
 Supplied Contents: Board(s)
1000
Order

1+:

$0

 ADC12DC080LFEB/NOPB-ND Datasheet
DC1350A-B DC1350A-B-ND DC1350A-B Linear Technology/Analog Devices
View more  Part Status: Active
 Number of A/D Converters: 1
 Number of Bits: 12
 Sampling Rate (Per Second): 25M
 Data Interface: Parallel
 Input Range: 2 Vpp
 Power (Typ) @ Conditions: 75mW @ 25MSPS
 Utilized IC / Part: LTC2226H
 Supplied Contents: Board(s)
 Base Part Number: LTC2226
2
Order

1+:

$128.52

 DC1350A-B-ND Datasheet
ADC10221EVAL ADC10221EVAL-ND ADC10221EVAL Texas Instruments
View more  Part Status: Obsolete
 Number of A/D Converters: 1
 Number of Bits: 10
 Sampling Rate (Per Second): 20M
 Data Interface: Parallel
 Input Range: 1 Vpp
 Utilized IC / Part: ADC10221
 Supplied Contents: Board(s)
1000
Order

1+:

$0

 ADC10221EVAL-ND Datasheet
Hot Searches: thyristor in parallel resistor in parallel parallel resistor resistor parallel parallel resistance parallel connector parallel diode thyristor thyristor three-phase thyristor parallel led driver ic parallel crystal oscillator parallel power capacitor voltage across resistor in parallel voltage divider with parallel resistor voltage regulator parallel resistor voltage divider resistor in parallel voltage resistor capacitors in parallel parallel resistor calculator resistor in parallel formula parallel voltage resistance