BF494_D27Z

Overview

The BF494_D27Z is a discontinued NPN silicon small-signal transistor manufactured by onsemi. It utilizes the TO-92-3 (TO-226AA) through-hole package. The device features a maximum collector-emitter voltage of 20 V and a continuous collector current rating of 30 mA. Maximum power dissipation is limited to 150 mW at an ambient temperature of 25°C. The junction temperature range extends from -55°C to +150°C, with storage temperatures spanning -55°C to +150°C. DC current gain (hFE) has a minimum specification of 67. The component is classified as a single bipolar junction transistor designed for general-purpose switching and amplification applications.

Feature Summary

• NPN silicon construction optimized for low-voltage signal processing
• Through-hole mounting capability via standard TO-92 leaded package
• Wide thermal operating range supporting extreme environmental conditions

Applications

• General-purpose low-frequency amplification circuits
• Small-signal switching applications in consumer electronics
• Audio pre-amplifier stages requiring low noise characteristics

Procurement Notes

This specific part number is officially obsolete and no longer in production. Verification of availability requires checking authorized distributors for remaining stock or identifying equivalent active components. Sourcing should focus on verified suppliers to ensure authenticity, as end-of-life items may have varying shelf lives or handling histories that impact reliability.

Selection Notes

Designers replacing this component must verify pinout compatibility and electrical limits against the target circuit requirements. The successor BF494 maintains identical electrical specifications but may differ in packaging suffixes or manufacturing origin. Ensure that any substitute device meets the required 20V breakdown voltage and 30mA current constraints while fitting the existing PCB footprint.

Part Context

The BF494 series represents a legacy line of NPN transistors widely used in analog signal conditioning. The D27Z suffix typically denotes a specific tape-and-reel packaging configuration for automated assembly. This component belongs to the broader family of small-signal BJTs, serving as a fundamental building block for discrete amplifier designs before the prevalence of integrated operational amplifiers.

Replacement Considerations

The BF494 is the direct functional equivalent. Verify that the replacement matches the TO-92 pinout configuration (Collector, Emitter, Base) to prevent circuit damage during installation.