BC637 NPN Transistor: Circuit, Pinout, and Datasheet
TRANS NPN 60V 1A TO-92
The BC637 is an NPN medium power transistor series. This article mainly introduces Circuit, Pinout, Datasheet and other detailed information about ON Semiconductor BC637.

Supercapacitor Joule Thief
BC637 Description
The BC637 is an NPN medium power transistor series. The BC637 is housed in a TO-92 plastic case. The emitter, collector, and base leads emerge from the transistor from left to right when looking at the flat side with the leads oriented downward.
BC637 Pinout
The following figure is BC637 Pinout.

Pinout
BC637 CAD Model
The BC637 CAD Model is shown as follows.

Symbol

Footprint

3D Model
BC637 Features
• These are Pb−Free Devices*
• High current
• Two current gain selections
• High power dissipation capability
• Collector-Emitter Volt (Vceo): 60V
• Collector Current (Ic): 1.0A
• hfe: 40 @ 160mA
• Power Dissipation (Ptot): 625mW
• Current-Gain-Bandwidth (ftotal): 200MHz
• Type: NPN
Specifications
- TypeParameter
- Lifecycle Status
Lifecycle Status refers to the current stage of an electronic component in its product life cycle, indicating whether it is active, obsolete, or transitioning between these states. An active status means the component is in production and available for purchase. An obsolete status indicates that the component is no longer being manufactured or supported, and manufacturers typically provide a limited time frame for support. Understanding the lifecycle status is crucial for design engineers to ensure continuity and reliability in their projects.
OBSOLETE (Last Updated: 1 week ago) - Mount
In electronic components, the term "Mount" typically refers to the method or process of physically attaching or fixing a component onto a circuit board or other electronic device. This can involve soldering, adhesive bonding, or other techniques to secure the component in place. The mounting process is crucial for ensuring proper electrical connections and mechanical stability within the electronic system. Different components may have specific mounting requirements based on their size, shape, and function, and manufacturers provide guidelines for proper mounting procedures to ensure optimal performance and reliability of the electronic device.
Through Hole - Mounting Type
The "Mounting Type" in electronic components refers to the method used to attach or connect a component to a circuit board or other substrate, such as through-hole, surface-mount, or panel mount.
Through Hole - Package / Case
refers to the protective housing that encases an electronic component, providing mechanical support, electrical connections, and thermal management.
TO-226-3, TO-92-3 (TO-226AA) - Number of Pins3
- Supplier Device Package
The parameter "Supplier Device Package" in electronic components refers to the physical packaging or housing of the component as provided by the supplier. It specifies the form factor, dimensions, and layout of the component, which are crucial for compatibility and integration into electronic circuits and systems. The supplier device package information typically includes details such as the package type (e.g., DIP, SOP, QFN), number of pins, pitch, and overall size, allowing engineers and designers to select the appropriate component for their specific application requirements. Understanding the supplier device package is essential for proper component selection, placement, and soldering during the manufacturing process to ensure optimal performance and reliability of the electronic system.
TO-92-3 - Weight201mg
- Collector-Emitter Breakdown Voltage60V
- Collector-Emitter Saturation Voltage500mV
- Current-Collector (Ic) (Max)1A
- Number of Elements1
- hFEMin40
- Operating Temperature
The operating temperature is the range of ambient temperature within which a power supply, or any other electrical equipment, operate in. This ranges from a minimum operating temperature, to a peak or maximum operating temperature, outside which, the power supply may fail.
-55°C~150°C TJ - Packaging
Semiconductor package is a carrier / shell used to contain and cover one or more semiconductor components or integrated circuits. The material of the shell can be metal, plastic, glass or ceramic.
Bulk - Published2002
- Part Status
Parts can have many statuses as they progress through the configuration, analysis, review, and approval stages.
Obsolete - Moisture Sensitivity Level (MSL)
Moisture Sensitivity Level (MSL) is a standardized rating that indicates the susceptibility of electronic components, particularly semiconductors, to moisture-induced damage during storage and the soldering process, defining the allowable exposure time to ambient conditions before they require special handling or baking to prevent failures
1 (Unlimited) - Termination
Termination in electronic components refers to the practice of matching the impedance of a circuit to prevent signal reflections and ensure maximum power transfer. It involves the use of resistors or other components at the end of transmission lines or connections. Proper termination is crucial in high-frequency applications to maintain signal integrity and reduce noise.
Through Hole - Max Operating Temperature
The Maximum Operating Temperature is the maximum body temperature at which the thermistor is designed to operate for extended periods of time with acceptable stability of its electrical characteristics.
150°C - Min Operating Temperature
The "Min Operating Temperature" parameter in electronic components refers to the lowest temperature at which the component is designed to operate effectively and reliably. This parameter is crucial for ensuring the proper functioning and longevity of the component, as operating below this temperature may lead to performance issues or even damage. Manufacturers specify the minimum operating temperature to provide guidance to users on the environmental conditions in which the component can safely operate. It is important to adhere to this parameter to prevent malfunctions and ensure the overall reliability of the electronic system.
-55°C - Voltage - Rated DC
Voltage - Rated DC is a parameter that specifies the maximum direct current (DC) voltage that an electronic component can safely handle without being damaged. This rating is crucial for ensuring the proper functioning and longevity of the component in a circuit. Exceeding the rated DC voltage can lead to overheating, breakdown, or even permanent damage to the component. It is important to carefully consider this parameter when designing or selecting components for a circuit to prevent any potential issues related to voltage overload.
60V - Max Power Dissipation
The maximum power that the MOSFET can dissipate continuously under the specified thermal conditions.
625mW - Current Rating
Current rating is the maximum current that a fuse will carry for an indefinite period without too much deterioration of the fuse element.
1A - Frequency
In electronic components, the parameter "Frequency" refers to the rate at which a signal oscillates or cycles within a given period of time. It is typically measured in Hertz (Hz) and represents how many times a signal completes a full cycle in one second. Frequency is a crucial aspect in electronic components as it determines the behavior and performance of various devices such as oscillators, filters, and communication systems. Understanding the frequency characteristics of components is essential for designing and analyzing electronic circuits to ensure proper functionality and compatibility with other components in a system.
100MHz - Base Part Number
The "Base Part Number" (BPN) in electronic components serves a similar purpose to the "Base Product Number." It refers to the primary identifier for a component that captures the essential characteristics shared by a group of similar components. The BPN provides a fundamental way to reference a family or series of components without specifying all the variations and specific details.
BC637 - Polarity
In electronic components, polarity refers to the orientation or direction in which the component must be connected in a circuit to function properly. Components such as diodes, capacitors, and LEDs have polarity markings to indicate which terminal should be connected to the positive or negative side of the circuit. Connecting a component with incorrect polarity can lead to malfunction or damage. It is important to pay attention to polarity markings and follow the manufacturer's instructions to ensure proper operation of electronic components.
NPN - Element Configuration
The distribution of electrons of an atom or molecule (or other physical structure) in atomic or molecular orbitals.
Single - Power Dissipation
the process by which an electronic or electrical device produces heat (energy loss or waste) as an undesirable derivative of its primary action.
1W - Power - Max
Power - Max is a parameter that specifies the maximum amount of power that an electronic component can handle without being damaged. It is typically measured in watts and indicates the upper limit of power that can be safely supplied to the component. Exceeding the maximum power rating can lead to overheating, malfunction, or permanent damage to the component. It is important to consider the power-max rating when designing circuits or systems to ensure proper operation and longevity of the electronic components.
625mW - Gain Bandwidth Product
The gain–bandwidth product (designated as GBWP, GBW, GBP, or GB) for an amplifier is the product of the amplifier's bandwidth and the gain at which the bandwidth is measured.
200MHz - Transistor Type
Transistor type refers to the classification of transistors based on their operation and construction. The two primary types are bipolar junction transistors (BJTs) and field-effect transistors (FETs). BJTs use current to control the flow of current, while FETs utilize voltage to control current flow. Each type has its own subtypes, such as NPN and PNP for BJTs, and MOSFETs and JFETs for FETs, impacting their applications and characteristics in electronic circuits.
NPN - Collector Emitter Voltage (VCEO)
Collector-Emitter Voltage (VCEO) is a key parameter in electronic components, particularly in transistors. It refers to the maximum voltage that can be applied between the collector and emitter terminals of a transistor while the base terminal is open or not conducting. Exceeding this voltage limit can lead to breakdown and potential damage to the transistor. VCEO is crucial for ensuring the safe and reliable operation of the transistor within its specified limits. Designers must carefully consider VCEO when selecting transistors for a circuit to prevent overvoltage conditions that could compromise the performance and longevity of the component.
60V - Max Collector Current
Max Collector Current is a parameter used to specify the maximum amount of current that can safely flow through the collector terminal of a transistor or other electronic component without causing damage. It is typically expressed in units of amperes (A) and is an important consideration when designing circuits to ensure that the component operates within its safe operating limits. Exceeding the specified max collector current can lead to overheating, degradation of performance, or even permanent damage to the component. Designers must carefully consider this parameter when selecting components and designing circuits to ensure reliable and safe operation.
1A - DC Current Gain (hFE) (Min) @ Ic, Vce
The parameter "DC Current Gain (hFE) (Min) @ Ic, Vce" in electronic components refers to the minimum value of the DC current gain, denoted as hFE, under specific operating conditions of collector current (Ic) and collector-emitter voltage (Vce). The DC current gain hFE represents the ratio of the collector current to the base current in a bipolar junction transistor (BJT), indicating the amplification capability of the transistor. The minimum hFE value at a given Ic and Vce helps determine the transistor's performance and efficiency in amplifying signals within a circuit. Designers use this parameter to ensure proper transistor selection and performance in various electronic applications.
40 @ 150mA 2V - Current - Collector Cutoff (Max)
The parameter "Current - Collector Cutoff (Max)" refers to the maximum current at which a transistor or other electronic component will cease to conduct current between the collector and emitter terminals. This parameter is important in determining the maximum current that can flow through the component when it is in the cutoff state. Exceeding this maximum cutoff current can lead to malfunction or damage of the component. It is typically specified in the component's datasheet and is crucial for proper circuit design and operation.
100nA ICBO - Vce Saturation (Max) @ Ib, Ic
The parameter "Vce Saturation (Max) @ Ib, Ic" in electronic components refers to the maximum voltage drop across the collector-emitter junction when the transistor is in saturation mode. This parameter is specified at a certain base current (Ib) and collector current (Ic) levels. It indicates the minimum voltage required to keep the transistor fully conducting in saturation mode, ensuring that the transistor operates efficiently and does not enter the cutoff region. Designers use this parameter to ensure proper transistor operation and to prevent overheating or damage to the component.
500mV @ 50mA, 500mA - Voltage - Collector Emitter Breakdown (Max)
Voltage - Collector Emitter Breakdown (Max) is a parameter that specifies the maximum voltage that can be applied between the collector and emitter terminals of a transistor or other semiconductor device before it breaks down and allows excessive current to flow. This parameter is crucial for ensuring the safe and reliable operation of the component within its specified limits. Exceeding the maximum breakdown voltage can lead to permanent damage or failure of the device. Designers and engineers must carefully consider this parameter when selecting components for their circuits to prevent potential issues and ensure proper functionality.
60V - Max Breakdown Voltage
The "Max Breakdown Voltage" of an electronic component refers to the maximum voltage that the component can withstand across its terminals before it breaks down and allows current to flow uncontrollably. This parameter is crucial in determining the operating limits and safety margins of the component in a circuit. Exceeding the maximum breakdown voltage can lead to permanent damage or failure of the component. It is typically specified by the manufacturer in datasheets to guide engineers and designers in selecting the appropriate components for their applications.
60V - Frequency - Transition
The parameter "Frequency - Transition" in electronic components refers to the maximum frequency at which a signal transition can occur within the component. It is a crucial specification for digital circuits as it determines the speed at which data can be processed and transmitted. A higher frequency transition allows for faster operation and better performance of the electronic component. It is typically measured in hertz (Hz) or megahertz (MHz) and is specified by the manufacturer to ensure proper functioning of the component within a given frequency range.
200MHz - Collector Base Voltage (VCBO)
Collector Base Voltage (VCBO) is the maximum allowable voltage that can be applied between the collector and base terminals of a bipolar junction transistor when the emitter is open. It is a critical parameter that determines the voltage rating of the transistor and helps prevent breakdown in the collector-base junction. Exceeding this voltage can lead to permanent damage or failure of the component.
60V - Emitter Base Voltage (VEBO)
Emitter Base Voltage (VEBO) is a parameter used in electronic components, particularly in transistors. It refers to the maximum voltage that can be applied between the emitter and base terminals of a transistor without causing damage to the device. Exceeding this voltage limit can lead to breakdown of the transistor and potential failure. VEBO is an important specification to consider when designing circuits to ensure the proper operation and reliability of the components. It is typically provided in the datasheet of the transistor and should be carefully observed to prevent any potential damage during operation.
5V - Height6.35mm
- Length6.35mm
- Width6.35mm
- REACH SVHC
The parameter "REACH SVHC" in electronic components refers to the compliance with the Registration, Evaluation, Authorization, and Restriction of Chemicals (REACH) regulation regarding Substances of Very High Concern (SVHC). SVHCs are substances that may have serious effects on human health or the environment, and their use is regulated under REACH to ensure their safe handling and minimize their impact.Manufacturers of electronic components need to declare if their products contain any SVHCs above a certain threshold concentration and provide information on the safe use of these substances. This information allows customers to make informed decisions about the potential risks associated with using the components and take appropriate measures to mitigate any hazards.Ensuring compliance with REACH SVHC requirements is essential for electronics manufacturers to meet regulatory standards, protect human health and the environment, and maintain transparency in their supply chain. It also demonstrates a commitment to sustainability and responsible manufacturing practices in the electronics industry.
No SVHC - RoHS Status
RoHS means “Restriction of Certain Hazardous Substances” in the “Hazardous Substances Directive” in electrical and electronic equipment.
Non-RoHS Compliant - Lead Free
Lead Free is a term used to describe electronic components that do not contain lead as part of their composition. Lead is a toxic material that can have harmful effects on human health and the environment, so the electronics industry has been moving towards lead-free components to reduce these risks. Lead-free components are typically made using alternative materials such as silver, copper, and tin. Manufacturers must comply with regulations such as the Restriction of Hazardous Substances (RoHS) directive to ensure that their products are lead-free and environmentally friendly.
Lead Free
Parts with Similar Specs
- ImagePart NumberManufacturerMountPackage / CasePolarityCollector Emitter Breakdown VoltageVoltage - Collector Emitter Breakdown (Max)Max Collector CurrentFrequency - TransitionCollector Emitter Saturation VoltagehFE MinMax Power DissipationView Compare
BC637
Through Hole
TO-226-3, TO-92-3 (TO-226AA)
NPN
60 V
60V
1 A
200MHz
500 mV
40
625 mW
Through Hole
TO-226-3, TO-92-3 (TO-226AA)
-
60 V
-
700 mA
-
200 mV
40
800 mW
Through Hole
TO-226-3, TO-92-3 (TO-226AA)
-
60 V
-
700 mA
-
200 mV
40
800 mW
Through Hole
TO-226-3, TO-92-3 (TO-226AA)
-
60 V
-
700 mA
-
200 mV
40
800 mW
BC637 Marking Diagrams
The following figure is BC637 Marking Diagrams.

Marking Diagrams
BC637 Circuit
After you've winded your transformer as shown in the video at the beginning of the article, all you have to do now is connect the components with 5 solder joints according to the schematic. Change the value of the base resistor to suit your needs, as explained in the video.

Circuit
BC637 Alternatives
| Part Number | Description | Manufacturer |
| BC637TRANSISTORS | Transistor | Bytesonic Corporation |
| BC637ZL1TRANSISTORS | Small Signal Bipolar Transistor, 0.5A I(C), 60V V(BR)CEO, 1-Element, NPN, Silicon, TO-92 | Motorola Semiconductor Products |
| BC637RLRBTRANSISTORS | 500mA, 60V, NPN, Si, SMALL SIGNAL TRANSISTOR, TO-92 | Motorola Mobility LLC |
| BC637RLTRANSISTORS | 500mA, 60V, NPN, Si, SMALL SIGNAL TRANSISTOR, TO-92 | Motorola Mobility LLC |
| BC637RLRATRANSISTORS | 500mA, 60V, NPN, Si, SMALL SIGNAL TRANSISTOR, TO-92, TO-226AA, 3 PIN | onsemi |
| BC637/D26ZTRANSISTORS | 1500mA, NPN, Si, SMALL SIGNAL TRANSISTOR, TO-92 | Texas Instruments |
| BC637/D27ZTRANSISTORS | 1500mA, NPN, Si, SMALL SIGNAL TRANSISTOR, TO-92 | Texas Instruments |
BC637 Applications
■ Linear voltage regulators
■ Low-side switches
■ MOSFET drivers
■ Amplifiers
BC637 Package
The following figure is BC637 Package.

Package
BC637 Manufacturer
ON Semiconductor ( Nasdaq : ON) is a disruptive technology firm that is helping to build a brighter future. It was founded in 1999. With an emphasis on automotive and industrial end-markets, the firm is speeding change in megatrends like as vehicle electrification and safety, sustainable energy grids, industrial automation, and 5G and cloud infrastructure. Through a highly specialized and unique product range, Onsemi provides intelligent power and sensor solutions that address the world's most pressing concerns and pave the path for a safer, cleaner, and smarter world.
Datasheet PDF
- PCN Obsolescence/ EOL :
- ReachStatement :
- Datasheets :
What is current gain in NPN transistor?
The current in a bipolar NPN transistor is the ratio of these two currents ( Ic/Ib ), called the DC Current Gain of the device, and is given the symbol of having or nowadays Beta, ( β ).
Why NPN transistor is most widely used?
The flowing of these electrons from emitter to collector forms the current flow in the transistor. Generally, the NPN transistor is the most used type of bipolar transistor because the mobility of electrons is higher than the mobility of holes.
What is the BC637?
An NPN medium power transistor series.
What type of plastic case is the BC637 housed in?
TO-92 plastic case.
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