BCY79-VII-TIN-LEAD - PNP 45V 100mA TO-18 BJT | Central Semiconductor
MPN: BCY79-VII-TIN-LEAD β Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $1.29 | $1.29 |
| 10 | $1.16 | $11.60 |
| 100 | $0.98 | $98.00 |
| 500 | $0.84 | $420.00 |
| 1,000 | $0.72 | $720.00 |
BCY79-VII-TIN-LEAD Overview
A bipolar junction transistor is a three-terminal current-controlled semiconductor device that amplifies or switches electronic signals. In the broader hierarchy, this small-signal PNP transistor sits within the discrete semiconductor family, complementing NPN devices for complementary push-pull stages and serving as a fundamental building block of analog signal chains in audio, industrial, and instrumentation electronics.
Key features of the BCY79-VII include its 45V VCBO breakdown rating, which provides generous headroom for 24V industrial rails; the low-noise characteristics that made the BCY79 family a classic choice for audio input and driver stages; the hermetic TO-18 metal can, which offers excellent thermal stability, light immunity, and moisture resistance far exceeding plastic packages; and the VI gain-group classification, denoting a specified DC current gain (hFE) bin as defined in the Central Semiconductor datasheet.
The planar epitaxial construction delivers stable gain and low leakage across the operating temperature range. The metal TO-18 case also provides a low thermal resistance path to the PCB, supporting the device's dissipation rating and reliable long-term operation in harsh environments where plastic-packaged alternatives would degrade.
Typical applications include low-noise audio amplifier input stages, driver stages, discrete analog signal conditioning, instrumentation front ends, and legacy industrial equipment maintenance where the original BCY79 family was designed-in decades ago. The tin/lead finish is especially valued for repair of legacy assemblies originally built with leaded solder.
Design consideration: verify the hFE bin (group VII) against your bias network, since the BCY79 family spans multiple gain groups (VI through X) with different hFE ranges; substituting across groups changes bias point and distortion performance.
This page synthesizes distributor availability data, drop-in alternatives, and practical design notes not found in the manufacturer datasheet, providing a single source of truth for engineers maintaining legacy designs.
Drop-in alternatives for BCY79-VII-TIN-LEAD β same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Quick Comparison Tool β Select alternative parts for side-by-side comparison:
BCY79-VII
β Drop-Inβ In Stock
$0.72 / Unit
View Datasheet βBCY79-VIII
β Drop-Inπ Reference alternative (not in catalog)
BCY79-VI
β Drop-Inπ Reference alternative (not in catalog)
BCY78-VII
β Drop-Inπ Reference alternative (not in catalog)
BCY78-VIII
β Drop-Inπ Reference alternative (not in catalog)
BCY79
β Drop-Inπ Reference alternative (not in catalog)
BCY79-VII-TIN-LEAD Maximum Ratings & Electrical Characteristics
| Transistor Type | PNP Bipolar Junction Transistor (BJT), Single |
| Technology | Silicon Planar Epitaxial |
| Collector-Base Voltage (VCBO) | 45 V |
| Emitter-Base Voltage (VEBO) | 5.0 V |
| Collector Current (IC) | 100 mA |
| Power Dissipation | 340 mW (derated), 1 W case-related rating per distributor listing |
| DC Current Gain Group | VII |
| Package | TO-18 metal can, 3-lead |
| Mounting Type | Through Hole |
| Finish | Tin/Lead (TIN/LEAD) plated leads |
| Polarity | PNP |
| Configuration | Single transistor |
| Typical Use | Low-noise audio amplifier input and driver stages |
| Manufacturer | Central Semiconductor Corp |
BCY79-VII-TIN-LEAD Pin Configuration
| Pin 1 | Emitter β Emitter terminal of PNP transistor |
| Pin 2 | Base β Base control terminal |
| Pin 3 | Collector β Collector terminal; case connected per datasheet |
Typical Applications
BCY79-VII-TIN-LEAD is suitable for 6 applications: Low-Noise Audio Input Stages, Audio Driver Stages, Legacy Industrial Equipment Maintenance, Instrumentation Signal Conditioning, Discrete Switching Circuits, Complementary Push-Pull Analog Stages.
Low-Noise Audio Input Stages
The BCY79-VII-TIN-LEAD was explicitly designed for audio input stages: the datasheet describes the BCY79 as a silicon planar epitaxial PNP transistor intended for audio input, driver, and low-noise input stages. Its hermetic TO-18 metal can shields the die from stray electric fields and light-induced noise, while the planar epitaxial process delivers stable, predictable hFE at the microamp-to-milliamp collector currents typical of phono preamps and microphone preamplifier first stages. With 45V VCBO, it tolerates higher supply rails than many small-signal PNPs, enabling higher dynamic range designs. Placed as the first amplifying device after the input coupling network, it sets the noise floor of the entire audio chain, which is why maintaining the VII gain group matters when repairing vintage equipment.
Recommended
Audio Driver Stages
As a driver stage device, the BCY79-VII-TIN-LEAD supplies base current to output transistors in class-AB audio amplifiers and discrete op-amp output sections. Its 100mA collector current rating covers the drive demands of most small power amplifier output pairs, and the 45V VCBO rating supports rails up to approximately 30V with safe margin. The TO-18 metal package provides a repeatable thermal environment, keeping bias currents stable as the amplifier warms up, which reduces output-stage drift and crossover distortion over time. The tin/lead finish ensures reliable joints in wave-soldered vintage-style assemblies. When repairing classic amplifiers designed around the BCY79 family, substituting within the same gain group preserves the original quiescent bias point and measured distortion performance.
Recommended
Legacy Industrial Equipment Maintenance
Many industrial control boards, test instruments, and process controllers built in the 1970s through 1990s used the BCY79 family as general small-signal PNP amplifiers and switches. The BCY79-VII-TIN-LEAD exists precisely for this repair market: Central Semiconductor manufactures it as a current-production clone of the original Philips part, and the tin/lead finish matches the leaded solder already on legacy boards, preventing the reliability problems that can occur when lead-free finishes meet leaded assembly processes. The hermetic TO-18 can has also proven highly durable, so replacing only the failed device preserves the rest of the board. Its 45V VCBO rating covers the 24V industrial logic rails common in that era of equipment.
Recommended
Instrumentation Signal Conditioning
In precision instrumentation front ends, the BCY79-VII-TIN-LEAD serves as a low-noise first-stage amplifier for sensor signals from thermocouple amplifiers, bridge conditioning circuits, and photodiode transimpedance stages. The planar epitaxial construction provides low base-spreading noise at the small collector currents used in high-impedance front ends, and the metal can package eliminates the photovoltaic and photoconductive effects that plastic packages can exhibit under ambient lighting. The 5.0V VEBO rating must be respected in reverse-biased input protection schemes, and the 45V VCBO permits front ends referenced to higher-voltage rails. Because bias stability directly affects offset drift, selecting the correct hFE group (VII) keeps the operating point within the design's drift budget across temperature.
Recommended
Discrete Switching Circuits
The NXP BCY79 heritage datasheet classifies the family as PNP switching transistors, and the BCY79-VII-TIN-LEAD remains well suited to discrete switching roles such as level shifting to negative rails, relay and LED drive from positive-supply logic, and power-rail load switches in mixed-signal boards. Its 100mA collector current handles typical relay coils and indicator loads, while the 45V VCBO accommodates inductive kickback when paired with a flyback diode. The TO-18 hermetic package performs reliably in high-humidity and thermally cycling environments where moisture ingress eventually degrades plastic-packaged transistors. Switching-speed figures are modest compared with modern digital transistors, so it is best used at low-to-moderate frequencies typical of legacy control logic.
Recommended
Complementary Push-Pull Analog Stages
The BCY79-VII-TIN-LEAD functions as the PNP half of complementary push-pull output and class-AB stages, paired historically with NPN devices of the same era. Matching gain groups between the NPN and PNP halves is the key design task: the VII bin ensures the PNP side delivers gain comparable to its NPN counterpart, minimizing crossover distortion and thermal runaway risk. The symmetric 45V VCBO and 100mA IC ratings allow both halves to be biased from the same rails, simplifying the bias network. In repaired or newly built discrete audio and servo amplifiers, the tin/lead finish supports traditional through-hole assembly used in hand-soldered prototypes and small-batch builds. Thermal coupling of both halves to a shared heatsink area further stabilizes the quiescent current.
Recommended
Recommended Products Summary
Engineering reference data for BCY79-VII-TIN-LEAD β comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | BCY79-VII | BCY79-VIII | BCY78-VII | BCY79 (NXP) |
|---|---|---|---|---|---|
| Package | TO-18 metal can | TO-18 - same | TO-18 - same | TO-18 - same | TO-18 - same |
| Brand | Central Semiconductor | Central Semiconductor | Central Semiconductor | Central Semiconductor | NXP Semiconductors |
| Polarity | PNP | PNP | PNP | PNP | PNP |
| VCBO | 45 V | 45 V | 45 V | 45 V | 45 V |
| Collector Current | 100 mA | 100 mA | 100 mA | 100 mA | 100 mA |
| Lifecycle Status | Active (legacy-vehicle) | Active | Active | Active | Discontinued |
Key Differentiators
- Tin/lead finish for legacy assembly (vs BCY79-VII (standard finish))
- Hermetic metal-can protection (vs Plastic-packaged PNP alternatives)
- Active production of a discontinued classic (vs BCY79 (NXP Semiconductors))
Design Notes
Do not substitute across hFE gain groups (VI/VII/VIII/IX/X) without re-verifying the bias network. The VII suffix denotes a specific DC current gain bin documented in the Central Semiconductor BCY78-79 datasheet; swapping to a BCY79-VIII shifts the operating point and can change distortion or switching thresholds. For vintage audio repairs, match the gain group printed on the original device before ordering a replacement.
The TO-18 metal can offers optional case grounding: depending on the datasheet internal connection, the case may be tied to the collector. Decide early whether the can will be grounded for shielding or isolated, since a grounded can touching adjacent traces or a metal chassis can short the collector. Maintain at least 2.5mm clearance around the can footprint and orient the tab so pin 1 (emitter) is correctly placed per the JEDEC TO-18 pinout: pin 1 emitter, pin 2 base, pin 3 collector.
Estimated: the 340mW dissipation rating constrains the safe operating area - at 45V VCBO, continuous collector current must stay far below 100mA (45V x 100mA = 4.5W, far exceeding 340mW). For a 24V rail design, keep quiescent dissipation under roughly 300mV x collector current products and derate above 25C ambient per the datasheet derating curve. Always provide a flyback diode when switching inductive loads such as relays to protect the 45V VCBO limit.
Compliance Information
This MPN is a deliberate tin/lead-finish (non-RoHS) variant intended for legacy leaded-solder assembly; the standard-finish BCY79-VII is the RoHS path. REACH and conflict-minerals status not stated in provided data.
