Smd Code Transistor: Types, Properties, and How It Enhances Industrial Performance

Types of SMD Code Transistors

A SMD (Surface Mount Device) transistor is a compact semiconductor device used in modern electronic circuits for switching and amplification. Due to their small footprint and compatibility with automated PCB assembly, SMD transistors are essential in consumer electronics, automotive systems, and communication devices. These transistors come in various types, each optimized for specific performance needs such as current handling, switching speed, and power efficiency.

Bipolar SMD Transistors

Bipolar junction transistors (BJTs) are widely used for signal amplification and switching due to their high current gain. Available in NPN and PNP configurations, they are ideal for both analog and digital circuits where precise control of current flow is required.

Advantages

• High current gain (hFE)
• Excellent for analog signal amplification
• Reliable in low-to-moderate power switching
• Cost-effective for general-purpose use

Limitations

• Lower input impedance compared to FETs
• Higher power consumption in some applications
• Sensitive to thermal runaway without proper biasing

Best for: Audio amplifiers, driver circuits, general-purpose switching

Field-Effect Transistors (FETs)

FETs are voltage-controlled devices with high input impedance, making them ideal for applications requiring minimal loading on the input signal. They are commonly used in RF circuits, impedance matching, and battery-powered systems due to their energy efficiency.

Advantages

• High input impedance
• Low power consumption
• Excellent for high-frequency applications
• Voltage-controlled operation

Limitations

• More sensitive to electrostatic discharge (ESD)
• Lower gain in some configurations
• Can be more expensive than BJTs

Best for: RF amplifiers, sensor interfaces, low-power digital circuits

MOSFETs (Metal-Oxide-Semiconductor FETs)

MOSFETs are the most widely used type of FETs, known for fast switching speeds and high efficiency. Available in enhancement and depletion modes, and in both N-channel and P-channel variants, they dominate power management, motor control, and digital logic circuits.

Advantages

• Very fast switching capability
• High efficiency in power applications
• Low on-resistance (Rds(on))
• Ideal for PWM and power regulation

Limitations

• Gate drive voltage requirements
• Potential for thermal instability at high loads
• Requires protection against voltage spikes

Best for: Power supplies, motor drivers, battery protection circuits

Common SMD Transistor Models and Specifications

Understanding key parameters such as Vce/Vds (voltage rating), Ic/Id (current capacity), and hFE (current gain) is crucial when selecting the right SMD transistor for a circuit design. Below is a detailed comparison of widely used models.

Type	Model	Voltage (V)	Current (A)	hFE / Notes	Application
Bipolar (NPN)	DTC123C	50 V	0.5 A	100–300	General switching, signal amplification
Bipolar (NPN)	DTC124C (DTC124N7)	50 V	0.7 A	100–300	Higher current switching
Bipolar (NPN)	DTC123Z	50 V	0.5 A	Typ. 200	Amplifier stages, driver circuits
MOSFET (N-Ch)	AP7360N	60 V	3.0 A	Low Rds(on), fast switching	Power management, DC-DC converters
MOSFET (N-Ch)	DPAK-AH3320	20 V	5.0 A	High current, compact package	Motor control, load switching
MOSFET (N-Ch)	GL1230N	30 V	4.5 A	Efficient low-voltage switching	Battery-powered devices
MOSFET (P-Ch)	KSF4040P	40 V	-3.0 A	High-side switching	Power rail control, reverse polarity protection
MOSFET (P-Ch)	STP6NK90Z	90 V	-6.0 A	High voltage, robust design	Industrial power systems
MOSFET (P-Ch)	PQ329P	25 V	-3.0 A	Compact, reliable switching	Portable electronics, power multiplexing

Expert Tip: Always verify the pinout configuration (e.g., SOT-23, SOT-323) when replacing SMD transistors, as different manufacturers may use varying layouts for the same code. Using a multimeter in diode test mode can help confirm transistor type and orientation before installation.

Design Note: For high-frequency switching applications, consider adding a small gate resistor (10–100Ω) to reduce ringing and EMI in MOSFET circuits. This improves reliability and electromagnetic compatibility.

Key Features of SMD Code Transistors

SMD (Surface Mount Device) code transistors are essential components in modern electronics, offering advanced performance and reliability in compact packages. Unlike older through-hole transistors such as NTE series devices, SMD transistors are engineered for high-density circuit integration, improved thermal management, and enhanced electrical efficiency. Their widespread adoption across industries—from consumer gadgets to automotive control systems—stems from a combination of innovative design and robust functionality.

Core Features and Benefits

Compact Design

SMD transistors are manufactured in miniature surface-mount packages such as SOT-23, SOT-89, and SC-70, enabling seamless integration into densely populated printed circuit boards (PCBs). Their small footprint allows for higher component density, which is critical in compact devices like smartphones, wearables, and IoT sensors.

Unlike bulky through-hole transistors that require drilling and take up significant board space, SMD variants are lightweight and ideal for automated pick-and-place assembly. This not only reduces manufacturing costs but also improves overall system portability and design flexibility.

High Performance

Modern SMD transistors deliver exceptional electrical performance, characterized by high switching speeds, low power consumption, and efficient heat dissipation. For example, SMD MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors) can switch on and off in nanoseconds, making them ideal for switch-mode power supplies (SMPS), DC-DC converters, and motor control circuits.

Their low on-resistance (R_DS(on)) minimizes energy loss during operation, improving overall system efficiency and reducing thermal buildup—critical for battery-powered and high-reliability applications.

Versatility Across Applications

SMD transistors come in a wide range of voltage and current ratings, allowing engineers to select the right component for diverse operating conditions. Low-power variants (e.g., small-signal transistors like 2N3904 in SOT-23) are commonly used in amplification and digital logic circuits.

At the same time, high-power SMD transistors and arrays are employed in automotive electronics (e.g., engine control units), industrial motor drivers, LED lighting systems, and power management modules. This versatility makes SMD transistors a universal choice across consumer electronics, telecommunications, automotive, and industrial automation sectors.

Durability and Environmental Resilience

Engineered for reliability, many SMD transistors are built to withstand harsh operating environments. They exhibit strong resistance to temperature extremes (typically rated from -55°C to +150°C), vibration, and electromagnetic interference (EMI), ensuring stable performance in demanding applications.

Some ruggedized versions are encapsulated with protective coatings or conformal sealing to resist moisture, dust, and corrosion—making them suitable for outdoor equipment, automotive under-hood systems, and marine electronics. This durability contributes to longer product lifespans and reduced maintenance requirements.

Feature	Technical Advantage	Common Applications
Compact Size (e.g., SOT-23)	Enables high-density PCB layouts and miniaturization	Smartphones, wearables, portable medical devices
Fast Switching Speed	Reduces switching losses and improves energy efficiency	Power supplies, inverters, motor controllers
Wide Voltage/Current Range	Supports both signal-level and power-level operations	Amplifiers, logic circuits, battery management
Thermal & EMI Resistance	Maintains stability in high-temperature or noisy environments	Automotive systems, industrial controls, outdoor electronics

Additional Advantages

Automated Manufacturing Compatibility: SMD transistors are designed for reflow soldering and automated assembly lines, significantly reducing production time and human error.

Improved Signal Integrity: Shorter leads and reduced parasitic inductance result in better high-frequency performance and lower noise.

Cost-Effective at Scale: Mass production and reduced material usage make SMD transistors more economical for large-volume electronics manufacturing.

Eco-Friendly Design: Lower power consumption and reduced material waste contribute to greener electronic products.

Note: When selecting SMD transistors, always verify the marking code (e.g., "MMBT3904" marked as "1A") using the manufacturer’s datasheet, as many SMD packages share similar codes. Incorrect identification can lead to circuit failure. Additionally, proper PCB layout and thermal management are crucial to fully leverage their performance benefits.

How to Choose SMD Code Transistors

Selecting the right Surface Mount Device (SMD) code transistor is crucial for ensuring circuit reliability, efficiency, and long-term performance. These compact components are widely used in modern electronics due to their small footprint and high integration capabilities. However, choosing the correct SMD transistor requires careful evaluation of several key electrical and functional parameters.

This guide outlines the most critical factors to consider when selecting an SMD transistor, helping you match the right component to your application—whether it's for power switching, signal amplification, voltage regulation, or high-frequency communication.

Function and Application

The intended function of the transistor is the primary consideration in selection. SMD transistors serve various roles depending on circuit design and system requirements.

• Switching: Used in digital circuits and power control systems to turn loads on/off efficiently (e.g., driving LEDs, relays, or motors)
• Signal Amplification: Essential in analog circuits such as audio preamplifiers or sensor interfaces where small input signals must be boosted
• Voltage Regulation: Found in linear regulators and low-dropout (LDO) circuits to maintain stable output voltages
• Impedance Buffering: Prevents loading effects by isolating high-impedance sources from low-impedance loads

Key insight: Bipolar Junction Transistors (BJTs) are often used for switching and amplification, while MOSFETs excel in high-efficiency switching applications.

Collector-Emitter Voltage (Vce(max))

The maximum voltage that can be applied between the collector and emitter terminals without causing breakdown is a critical safety parameter. Exceeding this value risks permanent damage.

• Select a transistor with a Vce(max) rating at least 20–50% higher than the circuit’s maximum operating voltage to ensure reliability
• For example, if your circuit operates at 12V, choose a transistor rated for at least 15–18V (e.g., 20V or 25V for added margin)
• High-voltage applications (e.g., power supplies, motor drivers) require transistors with elevated Vce ratings (60V, 100V, or more)
• Low-voltage logic circuits (3.3V or 5V) can use lower-rated transistors, enabling smaller packages and reduced cost

Critical note: Always account for voltage spikes or transients in inductive loads (e.g., motors, solenoids) when determining required voltage headroom.

Current Rating (Ic max)

The maximum collector current (Ic) specifies the highest continuous current the transistor can safely handle. Operating beyond this limit leads to overheating and potential failure.

• Ensure the transistor’s Ic rating exceeds the peak load current by a safe margin (ideally 1.5x to 2x)
• For example, a relay drawing 500mA should be driven by a transistor rated for at least 750mA–1A
• Consider pulsed vs. continuous current: some transistors support higher peak currents for short durations
• Higher current applications may require thermal management (e.g., PCB copper pours, heatsinking)

Design tip: Use Darlington pairs or MOSFETs for high-current applications where standard BJTs may not suffice.

Current Gain (hFE or β)

Current gain (hFE) measures how effectively a BJT amplifies base current into collector current. It is vital for amplification stages and efficient switching.

• Higher hFE values (e.g., 100–400) mean less base current is needed to control a given collector current, improving efficiency
• Low hFE transistors require more drive current, which can burden microcontrollers or logic gates
• hFE varies with temperature and collector current—always check the datasheet graphs for real-world performance
• For switching applications, ensure sufficient base current to drive the transistor into saturation (low Vce)

Pro tip: In amplifier circuits, select transistors with consistent hFE across units or consider feedback networks to stabilize gain.

Power Dissipation (Pd)

Power dissipation refers to the maximum amount of heat the transistor can safely dissipate without exceeding its junction temperature limit. It is calculated as P = Ic × Vce.

• Exceeding Pd causes thermal runaway and eventual failure, especially in confined spaces or high-ambient-temperature environments
• SMD packages (e.g., SOT-23, SOT-89, SOT-223) have limited thermal capacity—larger packages dissipate more heat
• Derate power handling at higher temperatures (check derating curves in datasheets)
• Use thermal vias and copper planes to improve heat transfer from the component to the PCB

Rule of thumb: Operate at no more than 50–70% of the rated Pd for reliable long-term performance.

Transition Frequency (fT or Cutoff Frequency)

The transition frequency (fT) indicates the maximum frequency at which the transistor can effectively amplify signals. Beyond fT, gain drops significantly.

• RF circuits (e.g., wireless transmitters, receivers) require transistors with high fT (hundreds of MHz to GHz range)
• Audio amplifiers typically operate below 20 kHz and can use transistors with moderate fT (e.g., 100–300 MHz)
• Switching power supplies (e.g., DC-DC converters) benefit from higher fT to minimize switching losses
• MOSFETs often outperform BJTs in high-frequency switching due to faster switching speeds and lower gate charge

Design insight: For high-frequency applications, also consider parasitic capacitances (Cob, Cib) and switching times (ton, toff).

Expert Recommendation: Always consult the manufacturer’s datasheet for detailed specifications, including temperature derating, safe operating area (SOA), and package thermal resistance. When in doubt, opt for a slightly over-specified transistor to ensure robustness and longevity. For prototyping, consider using universal transistors like the BC847 (NPN) or BC857 (PNP) in SOT-23 packages, which offer balanced performance across many general-purpose applications.

Application Type	Recommended Transistor Type	Typical Vce(max)	Min hFE / fT	Package Example
Low-power switching (LEDs, logic)	NPN BJT (e.g., BC847)	50V	hFE > 200	SOT-23
Audio amplification	Low-noise BJT (e.g., BC547)	30–50V	hFE > 300, fT > 150 MHz	SOT-23 or SOT-89
DC-DC converter switching	N-channel MOSFET (e.g., AO3400)	30V	fT > 500 MHz (fast switching)	SOT-23 or SOT-223
RF signal amplification	RF BJT/MOSFET (e.g., BFR92A)	12–20V	fT > 5 GHz	SOT-23 or SOT-323

Additional Selection Tips

• Package Size: Match the SMD footprint (SOT-23, SOT-89, etc.) to your PCB layout and assembly capabilities
• Polarity: Confirm whether you need NPN/PNP (BJT) or N-channel/P-channel (MOSFET)
• Leakage Current: Critical in battery-powered devices—choose low-Icbo transistors for minimal standby drain
• Tolerance & Consistency: Industrial and automotive applications demand tighter parameter tolerances and AEC-Q101 qualified parts
• Availability & Cost: Prefer commonly stocked transistors to avoid supply chain delays and reduce costs

How to Use SMD Code Transistor: Applications and Practical Insights

Surface Mount Device (SMD) code transistors are compact, efficient semiconductor components widely used in modern electronics due to their small footprint, reliability, and high performance. These transistors play a vital role in controlling current flow, amplifying signals, and switching operations across a vast range of electronic equipment. Understanding their applications helps engineers, technicians, and hobbyists make informed design and repair decisions.

Technical Note: SMD transistors are labeled with alphanumeric codes instead of full part numbers due to size constraints. Always refer to manufacturer datasheets or use SMD code lookup tools to identify the exact transistor type before replacement or integration into a circuit.

1. Car Amplifiers

In car audio systems, SMD transistors serve as key components in power amplification stages. They receive low-level audio signals from the head unit (such as a stereo or media player) and amplify them to drive speakers with sufficient power and clarity. By precisely modulating voltage and current through the transistor's base-emitter junction, these devices enable high-fidelity sound reproduction even at high volumes.

Modern Class D amplifiers utilize arrays of SMD transistors in push-pull configurations for efficient switching amplification, minimizing heat generation while maximizing output power. Their small size allows for compact amplifier designs ideal for space-constrained vehicle environments.

Troubleshooting Tip: In car amplifiers, overheating SMD transistors often indicate poor thermal management or short circuits. Always check solder joints, heat sinks, and surrounding components when diagnosing amplifier failures.

2. Telephony Systems (Telephone Systems)

SMD transistors are essential in both landline and VoIP telephony systems, where they perform dual roles in signal amplification and electronic switching. In analog phone lines, transistors boost weak voice signals to maintain clarity over long distances, reducing noise and distortion.

In digital telephone exchanges and PBX systems, SMD transistors act as fast-switching elements that route calls between multiple lines efficiently. Their rapid on/off response time ensures minimal delay in call setup and signal transmission, contributing to reliable communication networks.

• Used in line drivers and receivers for impedance matching
• Integrated into codec circuits for analog-to-digital signal conversion
• Enable echo cancellation and noise suppression in modern handsets

3. Computers and Other Digital Devices

SMD transistors form the backbone of digital logic circuits in computers, smartphones, tablets, and embedded systems. While microprocessors use millions of microscopic transistors on silicon dies, discrete SMD transistors support peripheral circuitry by managing power delivery, signal conditioning, and interface control.

They are commonly found in:

• Voltage regulation circuits (e.g., switching regulators using MOSFETs)
• Signal buffering and level shifting between ICs
• LED backlight drivers in displays
• GPIO expansion and relay control in motherboards and expansion cards

The relentless miniaturization of electronics has made SMD transistors indispensable in achieving higher component density without sacrificing performance or thermal efficiency.

4. Broadcasting Equipment

Television and radio transmitters rely heavily on SMD transistors in RF (Radio Frequency) amplification stages. These transistors amplify carrier signals to high power levels necessary for long-distance transmission while preserving signal integrity and minimizing harmonic distortion.

Advantages of SMD transistors in broadcasting include:

• Compact size enabling dense circuit layouts in transmitter modules
• Improved thermal performance when mounted on metal-core PCBs
• High-frequency operation suitable for VHF/UHF bands
• Reliability under continuous operation in broadcast environments

Common types include RF power MOSFETs and bipolar junction transistors (BJTs) optimized for high gain and low noise in transmitter front-ends.

5. RF Devices

Wireless communication systems such as cellular base stations, Wi-Fi routers, satellite transceivers, and IoT devices use SMD transistors for RF signal amplification, mixing, and switching. These transistors operate at high frequencies (MHz to GHz range) and must maintain linearity, low noise, and high efficiency.

Key applications include:

• Low-noise amplifiers (LNAs) at receiver inputs
• Power amplifiers (PAs) in transmission chains
• RF switches for antenna selection and mode switching
• Oscillator circuits for frequency generation

Their surface-mount design supports automated assembly and ensures consistent electrical performance in mass-produced wireless modules.

6. Everyday Appliances

SMD transistors are embedded in numerous household appliances, where they manage control logic, sensor interfacing, and power regulation. Examples include:

• Refrigerators: Controlling compressor cycles based on temperature sensor input
• Washing Machines: Regulating motor speed via PWM (Pulse Width Modulation) signals
• Microwaves: Driving magnetron control circuits and display backlights
• Air Conditioners: Managing fan speeds and compressor operation
• Smart Home Devices: Acting as switches for relays, LEDs, and wireless modules

Their durability, low power consumption, and resistance to vibration make SMD transistors ideal for consumer-grade appliances subject to daily use.

Application Area	Primary Function	Common SMD Transistor Types	Key Performance Requirements
Car Amplifiers	Audio Signal Amplification	Bipolar (NPN/PNP), Power MOSFETs	High current handling, low distortion
Telephony Systems	Signal Boosting & Switching	General-purpose BJTs, Small-signal FETs	Fast switching, linearity
Computers & Digital Devices	Power Control & Logic Switching	MOSFETs, Switching Transistors	High speed, low on-resistance
Broadcasting Equipment	RF Signal Amplification	RF Power Transistors, LDMOS	High gain, thermal stability
RF Devices	Amplification & Signal Switching	RF BJTs, GaAs FETs, PIN Diodes	High frequency, low noise
Everyday Appliances	Control & Power Management	General-purpose SMD Transistors	Durability, cost-effectiveness

Design Tip: When working with SMD transistors, always observe proper soldering techniques—use temperature-controlled irons or reflow ovens to avoid thermal damage. Consider using magnification tools to inspect solder joints and ensure reliable connections.

Best Practices for Using SMD Transistors

• Identify Correctly: Use SMD code books or online databases to decode markings and confirm device specifications (e.g., polarity, voltage rating, gain).
• Check Datasheets: Always consult manufacturer datasheets for pinout, thermal characteristics, and safe operating area (SOA).
• Thermal Management: Provide adequate copper pour or thermal vias on PCBs to dissipate heat, especially in power applications.
• ESD Protection: Handle SMD transistors with ESD-safe tools and workstations to prevent electrostatic damage.
• Circuit Testing: Test circuits incrementally and monitor current draw to catch potential shorts early.

Understanding how SMD code transistors function across various applications empowers engineers and technicians to design, troubleshoot, and repair electronic systems more effectively. As technology continues to evolve toward smaller, faster, and more energy-efficient devices, the role of SMD transistors will remain central to innovation in electronics.

Common Questions About SMD Code Transistors

Surface Mount Device (SMD) transistors are essential components in modern electronics, offering compact size and high efficiency. Below are some frequently asked questions that clarify key aspects of SMD transistors, helping engineers, hobbyists, and technicians make informed decisions in circuit design and repair.

Q1: What's the difference between a bipolar and a unipolar SMD transistor?

A1: The fundamental difference lies in how charge carriers operate within the semiconductor material:

• Bipolar Junction Transistors (BJTs): These rely on both electrons and holes (positive and negative charge carriers) for conduction. They are available in two configurations: NPN (where current flows from collector to emitter when base is forward-biased) and PNP (opposite polarity). BJTs are current-controlled devices and commonly used in amplification and switching applications.
• Unipolar Transistors (FETs – Field-Effect Transistors): These use only one type of charge carrier—either electrons (in N-channel) or holes (in P-channel). Examples include MOSFETs and JFETs. FETs are voltage-controlled, offering high input impedance and lower power consumption, making them ideal for digital circuits and power management systems.

Choosing between BJT and FET types depends on application requirements such as gain, switching speed, power efficiency, and control method.

Q2: Can SMD code transistors be used interchangeably?

A2: While some SMD transistors may appear similar in function or footprint, they should not be used interchangeably without careful consideration. Key reasons include:

• Marking Codes: SMD transistors often use alphanumeric codes (e.g., "MMBT3904") that are not standardized across manufacturers. The same code might refer to different devices depending on the brand.
• Electrical Parameters: Differences in voltage rating, current capacity, gain (hFE), switching speed, and power dissipation can lead to circuit malfunction or component failure if substituted incorrectly.
• Pin Configuration: Even with the same package (like SOT-23), pinouts may vary between manufacturers or transistor types (e.g., emitter-base-collector vs. source-gate-drain).
• Thermal Characteristics: Power handling and heat dissipation vary significantly between models.

Always consult the datasheet and verify exact specifications before replacing an SMD transistor. Cross-reference tools and manufacturer catalogs can help identify suitable equivalents.

Q3: How can I avoid damaging SMD transistors during installation?

A3: SMD transistors are sensitive to physical and electrical stress. Follow these best practices to prevent damage during soldering and assembly:

• Prevent Electrostatic Discharge (ESD): Always work on an ESD-safe workstation. Use grounded wrist straps, anti-static mats, and store components in conductive foam or bags.
• Use Temperature-Controlled Tools: Employ a soldering iron with adjustable temperature (typically 300–350°C) or a hot air rework station to avoid thermal shock. Excessive heat can degrade semiconductor junctions or damage internal structures.
• Minimize Soldering Time: Limit contact time to under 3 seconds per pad to prevent overheating.
• Proper Handling: Use fine-tipped tweezers to place components; avoid touching the leads directly with fingers to prevent contamination and static buildup.
• Inspect After Soldering: Check for bridging, misalignment, or cold joints that could affect performance.

Automated pick-and-place and reflow soldering systems are preferred in production environments for consistent, reliable results.

Q4: Why is proper SMD transistor selection critical in circuit design?

A4: Selecting the right SMD transistor is crucial for ensuring circuit performance, longevity, and reliability. Key factors include:

• Voltage and Current Ratings: The transistor must handle the maximum expected voltage (V_CE, V_DS) and current (I_C, I_D) without breakdown or overheating.
• Switching Speed: High-frequency applications (e.g., switching power supplies, RF circuits) require fast turn-on/turn-off times, which depend on transistor type and capacitance.
• Gain and Linearity: Amplifier circuits need transistors with stable current gain (hFE for BJTs, transconductance for FETs) across operating conditions.
• Power Dissipation: Ensure the package can dissipate heat effectively, especially in compact designs where thermal buildup is a concern.
• Package Size and PCB Compatibility: Match the footprint (e.g., SOT-23, SOT-89, SC-70) to your PCB layout and assembly process.

A well-chosen transistor improves efficiency, reduces heat generation, and enhances overall system stability—critical in battery-powered and high-reliability applications.

Q5: Are SMD transistors resistant to temperature variations?

A5: Most SMD transistors are designed to operate within specified temperature ranges, but their thermal resilience depends on several factors:

• Operating Temperature Range: Standard industrial-grade transistors typically function from -55°C to +150°C. Always check the datasheet for exact limits.
• Thermal Management: While SMD packages have limited surface area for heat dissipation, many include thermal pads or are mounted on copper pours to improve cooling. Some high-power variants (e.g., SOT-89, DPAK) are designed with enhanced thermal performance.
• Derating: Performance must be derated at higher temperatures—maximum current and power handling decrease as ambient temperature rises.
• Failure Risks: Prolonged exposure to excessive heat can cause parameter drift, junction degradation, or permanent failure. Conversely, extreme cold may affect carrier mobility and switching behavior.

To ensure reliability, design with adequate thermal margins, use heatsinks when necessary, and avoid placing transistors near high-heat components like power resistors or voltage regulators.