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onsemi BC548
- Part No.:
- BC548
- Manufacturer:
- onsemi
- Category:
- Single Bipolar Transistors
- Package:
- TO-226-3, TO-92-3 (TO-226AA)
- Datasheet:
-
BC548.pdf
- Description:
- TRANS NPN 30V 0.1A TO-92-3
- Quantity:
- Payment:
- Shipping:
Inventory:8,351
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Product details
Overview
BC548 from ON Semiconductor is an NPN epitaxial silicon transistor designed for general-purpose switching and amplification in low-power analog and digital circuits, with VCEO = 30 V, IC = 100 mA, PC = 500 mW, and hFE range of 420–800 (Class C), commonly used in audio preamplifiers, signal conditioning stages, and discrete logic interface circuits.
For engineers reviewing the BC548 datasheet, pinout, applications, or equivalent options, key selection criteria include DC current gain classification (C-grade), saturation voltage at 10 mA/0.5 mA drive, noise figure at 1 kHz, TO-92 thermal derating behavior, and compatibility with legacy BC-series bias networks.
Technical Context
The BC548 operates as a medium-gain, low-noise NPN bipolar junction transistor optimized for linear amplification and saturated switching in ambient-temperature-stable designs. Its hFE classification (C) ensures predictable gain matching in multi-stage amplifier chains, while its 30 V VCEO rating supports operation in 24 V rail systems with margin.
Thermal performance is defined by a 150 °C maximum junction temperature and 500 mW power dissipation at TA = 25 °C, requiring derating above 50 °C ambient. The device exhibits fT = 300 MHz at IC = 10 mA, enabling stable operation up to mid-VHF frequencies in small-signal applications.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCEO | 30 V - Maximum collector-emitter voltage before breakdown; sets safe operating limit in 24 V logic-level switching and low-voltage amplifier rails. |
| hFE (IC = 2 mA) | 420–800 - Class C DC current gain; enables high-input-impedance common-emitter stages with minimal base drive current. |
| VCE(sat) @ 10 mA/0.5 mA | 90–250 mV - Low saturation voltage ensures <1% voltage drop across collector-emitter path in switch-mode operation. |
| fT | 300 MHz - Current gain-bandwidth product; supports stable small-signal amplification up to ~100 MHz with proper biasing. |
| NF @ 1 kHz | 2.0–10.0 dB - Noise figure at 200 μA collector current; suitable for low-noise preamp stages in audio and sensor front-ends. |
| Cob | 3.5–6.0 pF - Output capacitance at 10 V VCB; limits high-frequency gain roll-off and affects stability in RF-coupled designs. |
Pinout & Package
BC548 is housed in a standard JEDEC TO-92 plastic package (3-lead, straight lead configuration), with 1.27 mm lead pitch and 4.57 mm body height. Thermal resistance RθJA is approximately 200 °C/W under free-air conditions.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (Top View, Flat Side Up) | Collector | Main current output terminal; connects to load or next stage input; requires heatsinking only above 200 mW dissipation. |
| 2 | Base | Control electrode; accepts low-current drive (typically ≤10% of IC) to regulate collector current flow. |
| 3 | Emitter | Current return path; often tied to ground or negative rail; establishes reference for VBE biasing network. |
Key Features
| Feature | Design Value |
|---|---|
| High DC current gain (hFE up to 800) | Reduces required base drive current by >5× compared to A/B-grade variants, lowering power consumption in battery-operated amplifiers. |
| Low VCE(sat) at moderate currents | Enables efficient switching in relay drivers and LED control circuits with <0.25 V conduction loss at 10 mA load. |
| Specified noise figure (2–10 dB) | Supports use in microphone preamplifiers and sensor signal conditioning where SNR degradation must remain below 10 dB. |
| TO-92 mechanical compatibility | Ensures drop-in replacement in legacy PCB footprints designed for BC546–BC550 family, simplifying BOM rationalization. |
Applications
| Audio Preamp Stage | Discrete Logic Level Shifter |
|---|---|
|
Use Scenario: Amplifying weak signals from electret microphones or piezoelectric sensors before ADC sampling. IC Role / Device Role / Timing Role: Small-signal NPN amplifier in common-emitter configuration with emitter degeneration. Use Value: Class C hFE provides consistent 40–50 dB voltage gain at 1–10 kHz without gain drift across production lots. |
Use Scenario: Translating 3.3 V logic outputs to 5 V or 12 V compatible levels for driving optocouplers or relays. IC Role / Device Role / Timing Role: Saturated switch with fixed base resistor network, operating in cutoff/saturation regions. Use Value: VCE(sat) ≤ 250 mV ensures <2% voltage error on 5 V loads, preserving TTL-compatible logic thresholds. |
| Linear Voltage Regulator Pass Element | Simple Oscillator Core (Phase Shift / Relaxation) |
|
Use Scenario: Acting as series pass transistor in low-dropout linear regulators for analog sensor supplies. IC Role / Device Role / Timing Role: Linear-mode current source controlled by op-amp feedback loop. Use Value: 30 V VCEO allows regulation of up to 24 V input rails with 2 V dropout margin at 100 mA load. |
Use Scenario: Building RC-based relaxation oscillators or phase-shift networks in function generators and timing circuits. IC Role / Device Role / Timing Role: Active gain element providing phase inversion and amplitude restoration in feedback loop. Use Value: fT = 300 MHz ensures stable oscillation up to 100 kHz without parasitic resonance or gain collapse. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar NPN general-purpose transistor applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| BC547C | Same TO-92 package and hFE class (C), but VCEO = 45 V and VCBO = 50 V vs. BC548's 30 V/30 V ratings. | Preferred where higher voltage headroom is needed (e.g., 36 V industrial sensors), but not drop-in in 30 V-limited designs due to different breakdown margins. | Select BC547C when VCEO > 30 V is required without changing layout; verify bias network stability at higher VCB. |
| 2N3904 | Higher VCEO = 40 V, lower hFE range (100–300), and tighter VBE(on) tolerance (0.6–0.75 V vs. BC548's 0.58–0.7 V). | Better suited for precision-switching applications with strict VBE consistency, but less effective in high-gain analog stages than BC548C. | Choose 2N3904 for digitally controlled switches needing repeatable turn-on; avoid in gain-critical audio paths where BC548C's higher hFE matters. |
Compared with BC547C and 2N3904, BC548 offers the highest hFE among common TO-92 NPN transistors at 30 V rating, making it optimal for low-base-drive amplification where voltage margin is constrained.
Availability
BC548 is available at Aetrix Electronics and suitable for audio preamplification, discrete logic interfacing, and linear regulator pass elements requiring stable component supply across prototyping, industrial control, and consumer electronics production.
Supply support for BC548 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.
Manufacturer
ON Semiconductor is a global semiconductor manufacturer specializing in energy-efficient power management, analog, and sensing solutions for automotive, industrial, and consumer markets.
The BC548 belongs to ON Semiconductor's legacy general-purpose bipolar transistor product line, originally developed by Fairchild and maintained for backward compatibility in cost-sensitive, high-volume linear and switching applications.
FAQ
What is the exact hFE range specified for BC548?
The BC548 is classified as Class C, with a guaranteed DC current gain (hFE) range of 420 to 800 when measured at VCE = 5 V and IC = 2 mA. This specification applies specifically to the BC548C variant, which matches the ordering code BC548CTA referenced in the datasheet.
Is BC548 pin-compatible with other BC-series transistors like BC547 or BC550?
Yes, BC548 shares identical TO-92 pinout (Collector-Base-Emitter, left-to-right with flat side facing up) and mechanical footprint with BC546 through BC550. However, electrical parameters differ-especially VCEO, VCBO, and noise figure-so direct substitution requires verification of voltage and gain requirements in the target circuit.
What is the maximum power dissipation for BC548 at 70°C ambient temperature?
BC548 has a rated PC = 500 mW at TA = 25 °C. With a typical thermal resistance RθJA ≈ 200 °C/W, power must be derated linearly above 25 °C: at 70 °C ambient, maximum allowable dissipation is 500 mW − (70−25) × (500/125) = 320 mW.
Does BC548 support low-noise operation in audio applications?
Yes, BC548 has a specified noise figure of 2.0–10.0 dB at VCE = 5 V, IC = 200 μA, f = 1 kHz, and RG = 2 kΩ. This makes it suitable for low-level audio preamplifier stages where noise contribution must remain below 10 dB, though BC549/BC550 offer lower noise for critical applications.
What packaging options are available for BC548?
The BC548CTA ordering code indicates TO-92 packaged devices supplied in ammo pack format. Other variants include BC548BU (bulk) and BC548BTA (ammo-pack with B-grade hFE). All share the same TO-92 outline and pin configuration, differing only in gain binning and packaging method.
BC548 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- onsemi
- Series:
- -
- Package/Case:
- TO-226-3, TO-92-3 (TO-226AA)
- Packaging:
- Bulk
- Product Status:
- Obsolete
- Transistor Type:
- NPN
- Current - Collector (Ic) (Max):
- 100 mA
- Voltage - Collector Emitter Breakdown (Max):
- 30 V
- Vce Saturation (Max) @ Ib, Ic:
- 600mV @ 5mA, 100mA
- Current - Collector Cutoff (Max):
- 15nA (ICBO)
- DC Current Gain (hFE) (Min) @ Ic, Vce:
- 110 @ 2mA, 5V
- Power - Max:
- 500 mW
- Frequency - Transition:
- 300MHz
- Operating Temperature:
- 150°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- TO-92-3
BC548 FAQ
1.How can I place an order for BC548 through Aetrix?
Please submit a Request for Quotation (RFQ) for BC548 on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for BC548 reliable?
The price and inventory of BC548 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BC548 is usually 5 days.
3.What payment methods are accepted for BC548?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BC548 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for BC548?
BC548 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your BC548 order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for BC548?
For technical support, including BC548 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BC548 requirements.
6.How does Aetrix verify that BC548 is sourced from the original manufacturer or authorized distributors?
All BC548 products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that BC548 meets industry standards.
7.What is the process for return or replacement of BC548?
All BC548 units undergo pre-shipment inspection (PSI). If there is an issue with BC548, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The BC548 part is unused and in its original packaging.
Return procedure for BC548:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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