NXP Semiconductors BF861B,215

Overview

BF861B,215 from NXP Semiconductors is an N-channel symmetrical junction field-effect transistor (JFET) in SOT23 package, designed for low-noise RF and audio preamplifier stages. It delivers 6–15 mA drain current (IDSS), 16–25 mS forward transfer admittance (|yfs|), and ultra-low input capacitance (Ciss ≤ 10 pF) at 1 MHz, enabling high-gain, wideband amplification in AM tuner front-ends.

For engineers reviewing the BF861B,215 datasheet, BF861B,215 pinout, BF861B,215 application, or BF861B,215 equivalent, this device is selected for low-noise small-signal amplification where gate-source cutoff voltage (VGSoff = −0.5 to −1.5 V), thermal resistance (Rth(j-a) = 500 K/W), and reverse transfer capacitance (Crss ≤ 2.7 pF) directly impact noise figure and stability in tuned RF circuits.

Technical Context

The BF861B,215 operates as a depletion-mode N-channel JFET with symmetrical source/drain terminals, allowing bidirectional signal handling in common-source or common-gate configurations. Its junction-based structure provides inherent low 1/f noise and stable DC biasing without gate current-critical for high-input-impedance amplifier nodes.

Designed for operation at VDS ≤ 25 V and IDSS = 6–15 mA, it features a gate-source breakdown voltage (V(BR)GSS) of −25 V and gate cut-off current (IGSS) ≤ −1 nA at VGS = −20 V, ensuring robust ESD resilience when handled per antistatic protocols. The device's Crss/Ciss ratio supports high reverse isolation in cascode or mixer topologies.

Key Specifications

Pinout & Package

SOT23 plastic surface-mounted package (TO-236AB), 3-lead, 1.3 mm × 2.9 mm × 1.0 mm body, with standard JEDEC outline and FR4 PCB mounting.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar low-noise JFET amplifier applications.

Compared with BF861B,215, BF862,215 offers higher gain and current capability at the cost of tighter VGSoff control, while J310 trades SMT compatibility and thermal performance for raw current headroom-making BF861B,215 optimal for compact, low-noise SOT23 preamplifier designs.

Availability

BF861B,215 is available at Aetrix Electronics and suitable for AM radio tuners, RF signal conditioning stages, and low-noise audio preamplifiers requiring stable component supply and consistent parametric performance across production batches.

Supply support for BF861B,215 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

NXP Semiconductors is a global semiconductor company headquartered in Eindhoven, Netherlands, specializing in secure connectivity solutions for automotive, industrial, and consumer applications.

The BF861B,215 belongs to NXP's discrete RF JFET product line, engineered specifically for low-noise, high-frequency small-signal amplification in broadcast and communications equipment.

FAQ

What is the maximum drain-source voltage rating for BF861B,215?

The BF861B,215 has a maximum drain-source voltage (VDS) rating of 25 V under DC conditions. This absolute maximum rating must not be exceeded to avoid permanent device damage, and operation should remain within recommended conditions specified in the datasheet for reliable long-term performance.

Does BF861B,215 require external gate protection circuitry?

Yes - the BF861B,215 gate is electrostatically sensitive. Although supplied in antistatic packaging, the gate-source input must be protected against static discharge during PCB handling and assembly using series gate resistors (typically 1–10 kΩ) and/or transient voltage suppressors in final circuit design.

How does the symmetrical structure of BF861B,215 affect circuit design?

The symmetrical source/drain construction of BF861B,215 allows interchangeable use of pins 1 and 2, enabling flexible implementation in cascode configurations, differential pairs, or bidirectional signal paths without altering biasing - reducing layout constraints and component count in compact RF designs.

What is the typical input noise voltage of BF861B,215 and at what frequency is it specified?

The BF861B,215 has a typical equivalent input noise voltage (Vn/√B) of 1.5 nV/√Hz at 1 MHz. This value is measured under standard conditions (Tj = 25 °C, VDS = 8 V, VGS = 0 V) and serves as a key metric for evaluating its suitability in low-noise preamplifier applications.

Can BF861B,215 be used in place of BF861A or BF861C without circuit modification?

No - BF861B,215 has distinct IDSS (6–15 mA) and |yfs| (16–25 mS) ranges compared to BF861A (IDSS = 2–6.5 mA) and BF861C (IDSS = 12–25 mA). Substituting without adjusting bias resistors or load impedances may shift operating point, gain, and noise performance outside target specifications.