BF861B,235

Overview

The BF861B,235 is an N-channel symmetrical junction field effect transistor (JFET) manufactured by NXP Semiconductors. It is housed in a SOT23 plastic surface-mounted package with three leads. The device features a drain-source voltage rating of 25 V and a total power dissipation of 250 mW at 25 °C ambient temperature. For the BF861B variant, the drain current (IDSS) ranges from 6 mA to 15 mA at VGS = 0 V and VDS = 8 V. The forward transfer admittance (|yfs|) is specified between 16 mS and 25 mS under the same conditions. Input capacitance is limited to 10 pF, while reverse transfer capacitance is typically 2.1 pF and up to 2.7 pF at 1 MHz.

Feature Summary

• High transfer admittance for effective signal amplification
• Low input and feedback capacitance suitable for high-frequency applications
• Low noise performance characterized by equivalent input noise voltage
• Integrated electrostatic discharge protection

Applications

• Preamplifiers for AM tuners in car radios

Procurement Notes

Verify the specific ordering suffix matches the required tape-and-reel quantity and manufacturing origin. Confirm RoHS compliance status and lead-free marking codes on the physical component against the datasheet revision. Ensure static-sensitive handling protocols are followed during storage and assembly due to the JFET gate sensitivity.

Selection Notes

Select the BF861B when a moderate drain current range of 6 mA to 15 mA is required compared to the lower IDSS of the BF861A or higher IDSS of the BF861C. Ensure the application operates within the 25 V drain-source voltage limit. Verify that the SOT23 package thermal resistance meets the system's heat dissipation requirements without exceeding the maximum junction temperature.

Part Context

This component belongs to the BF861 family of N-channel junction FETs, which includes variants A, B, and C differentiated primarily by their drain current and forward transfer admittance specifications. All variants share identical pinouts, package types, and voltage ratings, allowing for potential design flexibility based on gain and current requirements within the same footprint constraints.

Replacement Considerations

Direct pin-compatible substitutes within the same family include BF861A and BF861C, provided their respective IDSS and |yfs| ranges align with the circuit design tolerances. Cross-manufacturer replacements require careful verification of electrical parameters, particularly breakdown voltages and capacitance values, to ensure functional equivalence.

FAQ

What is the typical equivalent input noise voltage for the BF861B?

The typical equivalent input noise voltage is 1.5 nV/√Hz at a frequency of 1 MHz with VGS = 0 V.

How does the BF861B differ electrically from the BF861A?

The BF861B has a higher drain current range (6-15 mA vs 2-6.5 mA) and higher forward transfer admittance (16-25 mS vs 12-20 mS) compared to the BF861A, while sharing the same package and voltage ratings.

Is the BF861B automotive qualified?

No, unless explicitly stated otherwise in specific documentation, this product is not automotive qualified and is not tested according to automotive standards.