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onsemi BC33840BU
- Part No.:
- BC33840BU
- Manufacturer:
- onsemi
- Category:
- Single Bipolar Transistors
- Package:
- TO-226-3, TO-92-3 (TO-226AA)
- Datasheet:
-
BC33840BU.pdf
- Description:
- TRANS NPN 25V 0.8A TO-92-3
- Quantity:
- Payment:
- Shipping:
Inventory:3,345
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Product details
Overview
BC33840BU from ON Semiconductor is an NPN epitaxial silicon transistor in TO-92 package, rated for 30 V VCEO, 800 mA IC, and 625 mW power dissipation, with DC current gain (hFE) of 250–630 at IC = 100 mA, used in low-power amplifier and switching stages of consumer audio and signal conditioning circuits.
For engineers reviewing the BC33840BU datasheet, pinout, applications, or equivalent options, key selection criteria include its VCEO = 25 V rating, hFE classification (40), VCE(sat) ≤ 0.7 V at 500 mA/50 mA drive, and TO-92 thermal resistance of 200 °C/W - all critical for discrete gain stage and load-switch design validation.
Technical Context
The BC33840BU operates as a general-purpose NPN bipolar junction transistor optimized for linear amplification and saturated switching in low-voltage, medium-current applications. Its hFE range (250–630) supports stable biasing across production lots, while fT = 100 MHz enables use up to mid-frequency AF ranges.
Designed for compatibility with BC328 PNP complements, it features VEB0 = 5 V reverse emitter-base rating and Cob = 12 pF at 10 V, supporting predictable AC response in common-emitter configurations without external compensation in sub-10 MHz designs.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCEO | 25 V - Maximum collector-emitter voltage before breakdown under open-base conditions; defines safe operating voltage headroom in amplifier and switch topologies. |
| IC (DC) | 800 mA - Continuous collector current limit; sets maximum load drive capability in relay drivers or pre-driver stages. |
| hFE (IC = 100 mA) | 250–630 - DC current gain spread for BC33840BU classification; enables consistent bias point setting across manufacturing batches. |
| VCE(sat) | ≤ 0.7 V at IC = 500 mA, IB = 50 mA - Low saturation voltage minimizes conduction loss in switching applications. |
| fT | 100 MHz - Current gain bandwidth product; supports stable small-signal amplification up to ~10 MHz with adequate gain margin. |
| PD | 625 mW at TA = 25°C - Power dissipation limit defining thermal derating slope (5 mW/°C above 25°C) on standard FR-4 PCBs. |
Pinout & Package
BC33840BU is housed in a JEDEC TO-92 3-lead plastic package with straight leads (bulk packing). Pin 1 is Collector, Pin 2 is Base, Pin 3 is Emitter - verified per Fairchild BC337/BC338 Rev. 1.5 datasheet Figure 1 and ordering table.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | Collector | Main current output terminal; connects to load or next stage input; requires heatsinking consideration above 200 mW dissipation. |
| 2 | Base | Control input for current amplification; driven with ~50 mA base current for full saturation at 500 mA collector load. |
| 3 | Emitter | Current return path; typically grounded in common-emitter configuration or tied to load in emitter-follower setups. |
Key Features
| Feature | Design Value |
|---|---|
| Complementary pairing | Matched performance with BC328 PNP transistors for push-pull amplifier stages and differential pairs. |
| AF driver optimization | hFE > 250 at 100 mA ensures stable voltage gain in audio preamplifier stages without active bias compensation. |
| Low VCE(sat) | 0.7 V max enables <1% voltage drop across transistor in 5 V logic-level switching applications. |
| TO-92 thermal profile | RθJA = 200 °C/W allows operation up to 125°C ambient when dissipating 312 mW on standard PCB land patterns. |
Applications
| Audio Preamp Stage | Relay Driver Circuit |
|---|---|
|
Use Scenario: Amplifying microphone or line-level signals prior to ADC sampling in portable audio recorders. IC Role / Device Role / Timing Role: Discrete NPN transistor configured in common-emitter topology for voltage gain and impedance matching. Use Value: hFE ≥ 250 ensures ≥20 dB gain stability across temperature and supply variations without feedback trimming. |
Use Scenario: Driving 12 V, 400 mA coil relays from microcontroller GPIO pins in industrial control panels. IC Role / Device Role / Timing Role: Saturated switch providing low-loss current path between relay coil and ground. Use Value: VCE(sat) ≤ 0.7 V limits relay coil voltage drop to <6% of nominal, ensuring reliable pull-in at end-of-life battery voltages. |
| Low-Power Output Stage | Signal Level Shifting |
|
Use Scenario: Final gain stage in battery-powered headphone amplifiers delivering ≤50 mW into 32 Ω loads. IC Role / Device Role / Timing Role: Class-A biased NPN emitter follower for low-output-impedance buffering. Use Value: fT = 100 MHz supports flat frequency response up to 20 kHz with <0.1 dB ripple using minimal compensation. |
Use Scenario: Converting 3.3 V logic outputs to 5 V compatible levels for legacy peripherals in embedded gateways. IC Role / Device Role / Timing Role: Active pull-up switch translating logic high via collector-emitter conduction. Use Value: VCEO = 25 V provides 5× safety margin over 5 V rail, preventing latch-up during transient overvoltage events. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar NPN transistor applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| BC33825TA | Same TO-92 package and pinout; hFE = 160–400 (lower gain band); VCEO = 25 V identical. | Suitable where lower gain tolerance is acceptable, e.g., fixed-bias switching with higher base drive margin. | Select BC33825TA when tighter hFE distribution is not required and cost sensitivity favors standard-grade variant. |
| BC33740BU | Same hFE classification (40), but VCEO = 45 V and VCES = 50 V - higher voltage rating than BC33840BU's 25 V/30 V. | Required in 30–40 V supply rails where BC33840BU would exceed VCEO limit, e.g., automotive accessory modules. | Choose BC33740BU only if system voltage exceeds 25 V; otherwise BC33840BU offers better thermal efficiency at same gain. |
Compared with BC33825TA and BC33740BU, the BC33840BU delivers optimal balance of gain (250–630), low saturation voltage (≤0.7 V), and thermal performance (625 mW) for 5–12 V systems - making it preferred for precision AF amplification and compact relay drivers where both gain stability and conduction loss matter.
Availability
BC33840BU is available at Aetrix Electronics and suitable for audio preamplifier stages, relay driver circuits, and low-power output stages requiring stable component supply, consistent hFE binning, and TO-92 mechanical compatibility.
Supply support for BC33840BU 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 (formerly Fairchild Semiconductor) is a global supplier of energy-efficient semiconductor components, specializing in power management, analog, and discrete devices for industrial, automotive, and consumer markets.
The BC33840BU belongs to the BC337/BC338 family of general-purpose NPN transistors designed for cost-sensitive, high-volume applications requiring reliable switching and amplification in low-to-medium power circuits.
FAQ
What is the maximum collector-emitter voltage rating for BC33840BU?
The BC33840BU has a VCEO rating of 25 V, meaning it can safely withstand up to 25 V between collector and emitter with the base open. This rating is confirmed in the Absolute Maximum Ratings table of the BC337/BC338 Rev. 1.5 datasheet. Exceeding this voltage risks avalanche breakdown. For BC33840BU designs operating near this limit, derating by 20% is recommended for long-term reliability.
Does BC33840BU have a specified current gain (hFE) range, and how is it binned?
Yes, BC33840BU is classified as "hFE 40", indicating a guaranteed DC current gain range of 250–630 at VCE = 1 V and IC = 100 mA. This binning is defined in the hFE Classification table of the BC337/BC338 datasheet and applies specifically to BC33840BU - distinct from BC33825 (160–400) and BC33816 (100–250).
What is the thermal resistance (RθJA) of BC33840BU, and how does it affect PCB layout?
The BC33840BU has a junction-to-ambient thermal resistance (RθJA) of 200 °C/W under standard FR-4 PCB conditions (76 mm × 114 mm, minimum land pattern). This means a 625 mW power dissipation raises junction temperature by 125°C above ambient. To maintain TJ ≤ 150°C, ambient must stay below 25°C unless copper pour or thermal vias reduce effective RθJA.
Is BC33840BU pin-compatible with BC337 variants like BC33740BU?
Yes, BC33840BU shares identical TO-92 pinout (Collector-Base-Emitter on pins 1-2-3) and mechanical footprint with BC33740BU and all BC337/BC338 family members. However, they differ electrically: BC33840BU is rated for VCEO = 25 V, while BC33740BU supports 45 V - so direct substitution is only safe in ≤25 V circuits.
What packaging options are available for BC33840BU, and which is used for automated assembly?
BC33840BU is offered in bulk (BU) packaging, intended for manual or semi-automated insertion. For automated pick-and-place assembly, tape-and-reel (TFR) or ammo (TA) variants exist - but those are designated as BC33840TFR and BC33840TA, not BC33840BU. The BU suffix explicitly indicates bulk packaging with no carrier tape or ammo stick.
BC33840BU 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):
- 800 mA
- Voltage - Collector Emitter Breakdown (Max):
- 25 V
- Vce Saturation (Max) @ Ib, Ic:
- 700mV @ 50mA, 500mA
- Current - Collector Cutoff (Max):
- 100nA
- DC Current Gain (hFE) (Min) @ Ic, Vce:
- 250 @ 100mA, 1V
- Power - Max:
- 625 mW
- Frequency - Transition:
- 100MHz
- Operating Temperature:
- 150°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- TO-92-3
BC33840BU FAQ
1.How can I place an order for BC33840BU through Aetrix?
Please submit a Request for Quotation (RFQ) for BC33840BU 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 BC33840BU reliable?
The price and inventory of BC33840BU are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BC33840BU is usually 5 days.
3.What payment methods are accepted for BC33840BU?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BC33840BU transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for BC33840BU?
BC33840BU orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your BC33840BU 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 BC33840BU?
For technical support, including BC33840BU datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BC33840BU requirements.
6.How does Aetrix verify that BC33840BU is sourced from the original manufacturer or authorized distributors?
All BC33840BU 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 BC33840BU meets industry standards.
7.What is the process for return or replacement of BC33840BU?
All BC33840BU units undergo pre-shipment inspection (PSI). If there is an issue with BC33840BU, 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 BC33840BU part is unused and in its original packaging.
Return procedure for BC33840BU:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
BC33840BU Tags
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MMBT3906LT1G
onsemi
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MMBT3904-7-F
Diodes Incorporated
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onsemi
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MMBT3906-7-F
Diodes Incorporated
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MMBT3904-TP
Micro Commercial Co
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MMBT2222A-7-F
Diodes Incorporated
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BC846BLT1G
onsemi
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BC847B,215
Nexperia USA Inc.
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SMMBT3904LT1G
onsemi
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MMBT2222A-TP
Micro Commercial Co
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MMBTA06LT1G
onsemi
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MMBT2222ALT1G
onsemi
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