onsemi PN3640

Overview

PN3640 from ON Semiconductor is a PNP bipolar junction transistor designed for high-speed saturated switching in low-voltage logic interface and signal amplification circuits, with V_CEO = −12 V, I_C = −200 mA, f_T = 500 MHz, and V_CE(sat) = −0.20 V at I_C = −10 mA/I_B = −1.0 mA. It operates reliably from −55°C to +150°C and is commonly used in portable power management and digital output stage buffering.

For engineers reviewing the PN3640 datasheet, pinout, applications, or equivalent options, key selection criteria include its SOT-23 package footprint, PNP polarity, fast switching performance (t_on = 25 ns, t_off = 35 ns), low saturation voltage, and thermal resistance of 556°C/W on FR-4 PCB.

Technical Context

This device belongs to Fairchild's Process 65 high-speed BJT family and is optimized for saturated switching at collector currents up to −100 mA. Its design emphasizes minimal storage time (t_s = 20 ns) and low input/output capacitance (C_ib = C_ob = 3.5 pF), enabling clean edge transitions in TTL/CMOS-compatible driver stages.

The PN3640 exhibits DC current gain (h_FE) ranging from 30 to 120 at I_C = −10 mA/V_CE = −0.3 V, and maintains usable gain down to I_C = −50 mA (h_FE ≥ 20). Its −4 V V_EBO rating supports safe base-emitter reverse bias in open-collector configurations.

Key Specifications

Pinout & Package

SOT-23 (TO-236AB) 3-lead surface-mount package with gull-wing leads; compact 2.92 mm × 1.30 mm footprint and 1.20 mm max height. Marking "2J" identifies the PN3640 on-device.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar PNP switching amplifier applications.

Compared with MMBT3906 and DXT3640, the PN3640 delivers optimal balance of speed, saturation efficiency, and manufacturability in standard SOT-23 assembly lines-making it the preferred choice for new designs requiring ≤35 ns switching and ≤0.25 V dropout at −10 mA.

Availability

PN3640 is available at Aetrix Electronics and suitable for portable power management, logic interface translation, and digital output buffering requiring stable component supply, long-term lifecycle support, and traceable sourcing from ON Semiconductor's qualified production line.

Supply support for PN3640 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

ON Semiconductor is a global semiconductor manufacturer specializing in energy-efficient power management, analog, sensing, and connectivity solutions for automotive, industrial, cloud, and consumer markets.

The PN3640 originates from Fairchild's high-speed BJT portfolio, now integrated into ON Semiconductor's discrete transistor product line, targeting precision switching and signal conditioning in space-constrained, high-reliability applications.

FAQ

What is the maximum continuous collector current rating for the PN3640?

The PN3640 has a maximum continuous collector current (I_C) rating of −200 mA at T_A = 25°C. Derating is required above 25°C ambient per the 1.8 mW/°C thermal derating curve. At 65°C ambient, the effective I_C limit drops to approximately −175 mA to maintain junction temperature ≤150°C. The PN3640 must not be operated beyond this limit in sustained DC or high-duty-cycle applications.

Does the PN3640 support operation at elevated temperatures?

Yes, the PN3640 is rated for junction and storage temperatures from −55°C to +150°C. Its electrical characteristics-including h_FE, V_CE(sat), and leakage-are specified at 25°C and validated up to 65°C in the datasheet. For operation above 65°C, users must perform thermal analysis using R_θJA = 556°C/W and validate performance under actual board conditions, as parameters like I_CES increase significantly with temperature.

What is the base-emitter breakdown voltage (V_EBO) of the PN3640?

The PN3640 has a guaranteed minimum V_EBO of −4.0 V at I_E = −100 μA. This rating ensures safe reverse-bias operation when the base is driven negative relative to the emitter-common in open-collector or level-shifting configurations. Exceeding −4.0 V risks avalanche conduction and potential degradation of h_FE stability over time.

Can the PN3640 replace the MMBT3906 in existing designs?

The PN3640 is not a drop-in replacement for the MMBT3906 due to differences in switching speed and saturation voltage. While both are SOT-23 PNP transistors with identical pinout, the PN3640 offers faster t_off (35 ns vs. 70 ns) and lower V_CE(sat) (−0.20 V vs. −0.40 V). Substitution may improve performance but requires validation of timing margins and thermal behavior in the target circuit.

What is the typical current gain (h_FE) of the PN3640 at low collector current?

The PN3640 exhibits a typical DC current gain (h_FE) of 80–100 at I_C = −10 mA and V_CE = −0.3 V, with a guaranteed minimum of 30 and maximum of 120. At lower currents (e.g., I_C = −1 mA), h_FE rises but is not characterized in the official datasheet; design margins should assume h_FE ≥ 30 across the full operating range unless verified by bench testing.