Nexperia USA Inc. BF824,235

Overview

BF824,235 from Nexperia is a PNP medium-frequency transistor in SOT23 package, rated for −30 V V_CEO, −25 mA I_C, and 250 mW P_tot, optimized for RF amplification in FM front-end common-base configurations.

For engineers reviewing the BF824,235 datasheet, BF824,235 pinout, BF824,235 application, or BF824,235 equivalent, key selection factors include its f_T of 400–450 MHz at −4 mA, low Cre of 0.3 pF, and −900 mV V_BE at operating bias - critical for high-linearity, low-noise RF gain stages.

Technical Context

The BF824,235 operates as a PNP bipolar junction transistor with fixed-emitter common-base topology, supporting RF signal amplification up to 450 MHz transition frequency. Its low base-emitter voltage (−900 mV) and minimal feedback capacitance (0.3 pF) reduce Miller effect and improve stability in tuned amplifier designs.

Designed for DC-coupled or AC-coupled RF stages, it delivers h_FE = 25–50 across −1 to −8 mA collector current, with tight thermal resistance (R_th(j-a) = 500 K/W on FR4) enabling reliable operation in compact FM receiver modules.

Key Specifications

Pinout & Package

SOT23 plastic surface-mounted package (TO-236AB), 3-lead, dimensions per JEDEC MO-215AA: 2.9 × 1.3 × 1.0 mm, with 0.95 mm lead pitch and 0.1 mm minimum standoff.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar PNP medium-frequency transistor applications.

Compared with BC856B,215 and MMBT3906LT1G, the BF824,235 uniquely balances f_T > 400 MHz, C_re < 0.3 pF, and −30 V rating - making it the only drop-in solution for uncompensated, high-isolation FM front-end amplifiers in space-constrained designs.

Availability

BF824,235 is available at Aetrix Electronics and suitable for FM radio front-ends, portable audio receiver IF stages, and wireless microphone transmitter buffers requiring stable component supply and consistent RF performance across production batches.

Supply support for BF824,235 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

Nexperia is a global leader in discrete, logic, and PowerMOS semiconductors, spun off from NXP in 2017 and focused on automotive, industrial, computing, and consumer markets.

The BF824,235 belongs to Nexperia's RF bipolar transistor product line, engineered specifically for high-isolation, medium-frequency amplification in compact FM and wireless audio systems.

FAQ

Is BF824,235 suitable for common-emitter RF amplifier configurations?

No - the BF824,235 is characterized and optimized for common-base operation, where its low C_re and high f_T deliver best stability and gain. In common-emitter mode, its Miller capacitance increases significantly, risking oscillation above 50 MHz without neutralization.

What is the maximum recommended PCB copper area for thermal relief on the SOT23 pad?

For FR4 boards, Nexperia specifies R_th(j-a) = 500 K/W with no added copper; adding ≥25 mm² of 1-oz copper connected to the collector pad (Pin 3) reduces R_th(j-a) to ~320 K/W, enabling full 250 mW dissipation at +60 °C ambient.

Does BF824,235 require external bias stabilization for FM front-end use?

Yes - while h_FE is stable across current, the −900 mV V_BE exhibits −2.2 mV/°C temperature coefficient. A simple emitter resistor (e.g., 100 Ω) provides sufficient negative feedback to hold I_C within ±5% over −25 to +70 °C.

Can BF824,235 replace BF199 in legacy FM tuner designs?

No - BF199 is an NPN transistor with different bias polarity, pinout (emitter-collector swap), and higher f_T (≥600 MHz). Direct substitution would invert biasing and degrade gain; redesign of base/emitter networks and layout is required.