BCY79-VII PBFREE - PNP 45V 100mA TO-18 BJT | Central Semiconductor
MPN: BCY79-VII-PBFREE β End of Life| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $0 | $0.00 |
| 10 | $0 | $0.00 |
| 100 | $0 | $0.00 |
| 500 | $0 | $0.00 |
| 1,000 | $0 | $0.00 |
BCY79-VII-PBFREE Overview
A bipolar junction transistor is a three-terminal current-controlled semiconductor device that amplifies or switches electronic signals. Within the power and signal-chain hierarchy, the BJT sits under the discrete semiconductor family, alongside MOSFETs and IGBTs. The BCY79-VII is a small-signal PNP general purpose transistor intended for low-noise amplifier and medium-speed switching stages, complementing its NPN counterpart families in discrete front-end designs.
Key features include a 45 VCBO collector-base rating, a 5.0 VEBO emitter-base rating for input-stage robustness, a 100 MHz transition frequency supporting audio through RF-front-end switching roles, and a hermetically sealed TO-18 metal can that provides superior moisture immunity and thermal stability compared with plastic packages, making it attractive for harsh-environment and instrumentation designs.
Technically, the BCY79-VII uses an epitaxial planar silicon process. The metal TO-18 case (JEDEC TO-18 outline) acts as an electrostatic and electromagnetic shield, reducing stray noise pickup in low-noise input stages. The VII suffix designates a specific DC current gain (hFE) grouping within the BCY79 family; gain-grouped parts let designers lock gain windows across production lots, improving repeatability of bias points in discrete amplifier designs.
Typical applications include low-noise preamplifier input stages, analog instrumentation front ends, legacy industrial equipment service and repair, audio signal conditioning, and general purpose switching where a hermetic PNP device is required. Its availability as a Central Semiconductor remanufacture of an industry-standard type makes it a go-to part for maintaining legacy European-origin BCY79 bill-of-materials.
Design considerations: verify the pin mapping against the TO-18 drawing before layout, as BCY79-family pin order (emitter-base-collector with case tied to collector) differs from many other TO-18 transistors; derissipation above 340 mW free-air requires consideration of the 1 W case rating.
This page synthesizes distributor pricing, drop-in alternatives, pinout data, and practical design notes not consolidated in the manufacturer datasheet.
Drop-in alternatives for BCY79-VII-PBFREE 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-VIII PBFREE
β Drop-Inπ Reference alternative (not in catalog)
BCY79-IX PBFREE
β Drop-Inπ Reference alternative (not in catalog)
BCY79 PBFREE
β Drop-Inπ Reference alternative (not in catalog)
BCY78-VII PBFREE
β Drop-Inπ Reference alternative (not in catalog)
BCY79-9
β Drop-Inπ Reference alternative (not in catalog)
BCY79-VII-PBFREE Maximum Ratings & Electrical Characteristics
| Transistor Type | PNP Bipolar Junction Transistor (BJT) |
| Collector-Base Voltage (VCBO) | 45 V |
| Emitter-Base Voltage (VEBO) | 5.0 V |
| Collector Current (IC) | 100 mA |
| Transition Frequency (fT) | 100 MHz |
| Power Dissipation (PD, case) | 1 W |
| Power Dissipation (PD, free air) | 340 mW |
| Package | TO-18 (hermetically sealed metal can, through hole) |
| Mounting Type | Through Hole |
| Configuration | Single transistor |
| Technology | Silicon epitaxial planar |
| Feature | Low noise, general purpose amplifier and switching |
| Pb-Free Status | PBFREE (lead-free) |
| RoHS Status | Compliant (PBFREE suffix) |
BCY79-VII-PBFREE Pin Configuration
| Pin 1 | Emitter β Emitter terminal of PNP transistor |
| Pin 2 | Base β Base control terminal |
| Pin 3 | Collector β Collector terminal; internally connected to the metal TO-18 case |
| Pin C | Case β Hermetic metal can, connected to collector, provides electrostatic shielding |
Typical Applications
BCY79-VII-PBFREE is suitable for 6 applications: Low-Noise Preamplifier Input Stages, Analog Instrumentation Front Ends, Legacy Industrial Equipment Repair and Maintenance, Audio Signal Conditioning and Buffering, General Purpose Medium-Speed Switching, RF and IF Front-End Circuits.
Low-Noise Preamplifier Input Stages
The BCY79-VII PBFREE was explicitly designed by Central Semiconductor for low-noise amplifier applications. Its silicon epitaxial planar process and the electrostatically shielding hermetic TO-18 metal can reduce hum and stray pickup at sensitive input nodes, while the 100 MHz transition frequency provides ample closed-loop gain margin at audio frequencies. In a typical first-stage PNP common-emitter preamp, the gain-grouped VII hFE window keeps bias points repeatable across production lots. Because the transistor handles only small signals, the 100 mA / 340 mW ratings are far from their limits, maximizing reliability; place a base-stop resistor (100 ohm to 1 kohm) and keep the metal case, tied to collector, at AC ground for best noise performance.
Recommended
Analog Instrumentation Front Ends
Bench and industrial measurement equipment benefits from the BCY79-VII PBFREE's hermetic metal TO-18 package, which resists moisture ingress and provides electrostatic shielding unavailable in plastic TO-92 devices. The 45 V VCBO and 5.0 V VEBO ratings give headroom for higher-voltage analog rails common in instrumentation, and the 100 MHz fT supports fast settling in buffer and level-shift stages ahead of ADCs. Gain-grouped hFE (VII) improves long-term drift behavior of bias networks in DC-coupled front ends. Designers should keep VCE x IC products under the 340 mW free-air rating and degenerate emitters slightly (tens of ohms) to linearize gain and reduce thermal feedback in precision paths.
Recommended
Legacy Industrial Equipment Repair and Maintenance
The BCY79 family originated as a European industry-standard PNP used extensively in industrial controls, test gear, and audio equipment from the 1970s-1990s. Because the original-type production is discontinued, Central Semiconductor's remanufactured BCY79-VII PBFREE in the authentic JEDEC TO-18 hermetic can is a primary service part, restoring original mechanical form, pinout, and shielding. Maintenance engineers should stock gain groups VII, VIII, and IX to match hFE windows in existing designs, and verify the emitter-base-collector pin order with the tab reference before replacement, since other TO-18 families use different pin sequences. Current distributor stock (8840 pcs reported November 2025) supports ongoing service programs.
Recommended
Audio Signal Conditioning and Buffering
In audio paths, the BCY79-VII PBFREE serves as a low-noise input transistor, emitter-follower buffer, or phase splitter in discrete and hybrid amplifier architectures. The 100 MHz transition frequency yields a gain-bandwidth product far above the audio band, keeping distortion low from negative feedback even at the upper end of the audio range, and the metal can shields the input stage from power-supply hum. The PNP polarity conveniently suits direct coupling to grounded-emitter NPN stages in complementary line drivers. Designers should bias the collector current at 1-5 mA for optimal noise figure in the audio band and ensure the VEBO limit of 5.0 V is respected in high-swing stages by adding a base-emitter clamp.
Recommended
General Purpose Medium-Speed Switching
With a 100 MHz transition frequency and 100 mA collector current rating, the BCY79-VII PBFREE handles general purpose switching tasks such as driving small relays, LEDs, and analog switches, and level translation in mixed analog systems. The hermetic TO-18 package ensures stable switching thresholds in humid or thermally cycling environments where plastic packages degrade. Saturating the transistor at forced-beta of roughly 10 gives low VCE(sat) and fast turn-off with a modest base discharge network; a 1 kohm base-to-emitter resistor speeds recovery. Keep switched loads within the 340 mW free-air dissipation envelope, or exploit the 1 W case rating only with confirmed case-temperature mounting.
Recommended
RF and IF Front-End Circuits
The 100 MHz fT of the BCY79-VII PBFREE permits use in intermediate-frequency amplifiers, oscillator stages, and low-VHF mixer/AGC circuits in receivers and test equipment. The metal TO-18 can acts as a small Faraday shield, improving isolation between the transistor and neighboring magnetic components in crowded RF layouts - an advantage over plastic-packaged alternatives. Ground the case (collector) plane directly at the mounting point to minimize parasitic feedback. Gain-group selection (VII) stabilizes bias across lots in AGC-controlled stages. Expect useful gain up to several tens of megahertz; for operation approaching 100 MHz, verify actual gain at the chosen collector current using the manufacturer datasheet curves.
Recommended
Recommended Products Summary
Engineering reference data for BCY79-VII-PBFREE β comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | BCY79-VIII PBFREE | BCY79-IX PBFREE | BCY79 PBFREE | BCY78-VII PBFREE | BCY79-9 |
|---|---|---|---|---|---|---|
| Package | TO-18 (hermetic metal, through hole) | TO-18 - same | TO-18 - same | TO-18 - same | TO-18 - same | TO-18 - same (verify tab orientation) |
| Brand | Central Semiconductor | Central Semiconductor | Central Semiconductor | Central Semiconductor | Central Semiconductor | NXP Semiconductors |
| Polarity | PNP | PNP | PNP | PNP | PNP | PNP |
| VCBO | 45 V | 45 V | 45 V | 45 V | 45 V | 45 V class (verify exact limit) |
| Collector Current | 100 mA | 100 mA | 100 mA | 100 mA | 100 mA | 100 mA class (verify) |
| hFE Gain Group | VII group | VIII group | IX group | Generic / non-grouped | VII group (BCY78 series) | Group 9 (NXP scheme) |
Key Differentiators
- Hermetically sealed metal TO-18 can with shielding (vs BCY79 PBFREE)
- Gain-group selection window (VII) (vs BCY79-IX PBFREE)
- Lead-free (PBFREE) construction with legacy die (vs BCY79-9)
Design Notes
Verify TO-18 pin order before layout: the BCY79 family uses emitter-base-collector with the metal case tied to the collector, which differs from several other TO-18 transistor families. Reference the mechanical drawing in the Central Semiconductor BCY78-79 datasheet and locate the tab/keyway. Because the can is collector-connected, provide an isolated mounting hole if the shield is to be grounded separately from the collector node, or exploit the collector-shield connection to reduce capacitive pickup.
Respect the dual dissipation rating: 340 mW in free air versus 1 W at the case. Estimated: at IC = 50 mA and VCE = 10 V, dissipation is 500 mW, which exceeds the free-air rating and requires assurance of the case-temperature conditions behind the 1 W figure. Keep small-signal operating points below 340 mW (e.g., 20 mA at 10 V = 200 mW) to avoid heatsink considerations, and derate for elevated ambient temperature per the datasheet derating curve.
The BCY79-VII is End of Life per the Central Semiconductor datasheet PDF, which warns that customer demand sustainability led to discontinuation. Do not release it into new long-life production without a second-source or a qualified gain-group sibling (BCY79-VIII/IX, identical ratings and package, differing only in hFE window). Also note the 5.0 V VEBO limit is low compared with modern small-signal PNPs - clamp the base-emitter junction in high-swing or inductive-switching circuits to prevent reverse breakdown.
Compliance Information
PBFREE suffix denotes lead-free construction; DigiKey lists the part in RoHS-compliant categories. REACH, halogen-free and conflict-minerals declarations were not present in the retrieved data - verify on the Central Semiconductor product page.
