onsemi MPSH34

Overview

MPSH34 from Fairchild Semiconductor is an NPN general-purpose RF amplifier transistor optimized for low-noise common-emitter amplifier and mixer applications up to 300 MHz, with V_CEO = 40 V, I_C = 50 mA continuous, f_T = 500 MHz, and C_cb = 0.32 pF at 10 V - deployed in VHF oscillator circuits driving FET mixers.

For engineers reviewing the MPSH34 datasheet, pinout, applications, or equivalent options, key selection considerations include its 500 MHz f_T, 0.32 pF collector-base capacitance, 0.5 V V_CE(sat) at I_C = 7 mA/I_B = 2 mA, TO-92 package thermal resistance (R_θJA = 200 °C/W), and suitability for low-drift VHF oscillator designs.

Technical Context

The MPSH34 operates as a silicon NPN bipolar junction transistor with a common-emitter configuration optimized for RF amplification and mixing. Its high f_T (500 MHz) and low C_cb (0.32 pF) support stable gain up to 300 MHz, while its V_CE(sat) of 0.5 V enables efficient switching in oscillator driver stages.

Designed for low-frequency drift in common-base VHF oscillators, it delivers high output levels suitable for direct FET mixer drive. The device uses Fairchild's Process 47 and shares characterization context with the MPSH11 family, though exhibits distinct h_FE range (15–40) and thermal derating (5.0 mW/°C above 25°C).

Key Specifications

Pinout & Package

Package: TO-92 - Three-lead through-hole plastic package with standard lead spacing (1.27 mm pitch), 14.47 mm body length, and 3.60 mm width; rated for 625 mW total dissipation at 25°C ambient.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar NPN RF amplifier applications.

Compared with MPQ2222A and 2N5172, the MPSH34 offers balanced VHF gain-bandwidth (500 MHz f_T), 40 V breakdown margin, and proven stability in low-drift oscillator designs - making it preferred for 30–150 MHz FET mixer drivers where voltage headroom and thermal predictability matter.

Availability

MPSH34 is available at Aetrix Electronics and suitable for VHF oscillator drivers, low-noise RF amplifiers, RF mixer stages, and general-purpose signal switching applications requiring stable component supply across industrial, communications, and test equipment programs.

Supply support for MPSH34 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

Fairchild Semiconductor was a U.S.-based semiconductor manufacturer specializing in analog, discrete, and power management ICs before its acquisition by ON Semiconductor in 2016.

The MPSH34 belongs to Fairchild's FACT Quiet Series™ RF transistor family, engineered specifically for low-noise, low-drift VHF amplifier and oscillator applications demanding predictable gain and thermal behavior.

FAQ

What is the maximum operating frequency for the MPSH34 in amplifier configurations?

The MPSH34 has a current gain bandwidth product (f_T) of 500 MHz, and its usable small-signal gain extends reliably up to 300 MHz in common-emitter amplifier configurations. Performance beyond this depends on circuit layout, biasing, and load impedance - the MPSH34 datasheet confirms stable operation in 30–300 MHz VHF applications, especially when used with proper neutralization and impedance matching networks.

Does the MPSH34 support common-base oscillator topologies?

Yes, the MPSH34 is explicitly designed for low-frequency drift common-base VHF oscillator applications, as stated in its official Fairchild documentation. Its low C_cb (0.32 pF), consistent V_BE(on) (0.95 V), and thermal characteristics make it suitable for stable tank-circuit oscillators driving FET mixers - the MPSH34 functions effectively in common-base mode with high output level and minimal drift.

What is the safe continuous collector current rating for the MPSH34?

The MPSH34 is rated for a continuous collector current (I_C) of 50 mA at T_A = 25°C. Derating is required above ambient temperature: total device dissipation drops by 5.0 mW per °C rise, limiting usable I_C under elevated temperatures. This rating assumes proper PCB copper area and still-air conditions - the MPSH34's R_θJA of 200 °C/W must be considered in thermal design.

Is the MPSH34 pin-compatible with other TO-92 NPN transistors like the 2N3904?

No - although both use TO-92 packages, the MPSH34 pinout (1=Base, 2=Emitter, 3=Collector) differs from the 2N3904 (1=Emitter, 2=Base, 3=Collector). Swapping them without board revision will cause functional failure. Always verify pin assignment using the official MPSH34 datasheet - the MPSH34's defined pinout is integral to its RF layout integrity and thermal path design.

Can the MPSH34 replace the MPSH11 in existing designs?

The MPSH34 and MPSH11 share process and application focus, but they are not interchangeable without validation: the MPSH34 has higher f_T (500 MHz vs. ~300 MHz), tighter C_cb (0.32 pF vs. ~0.5 pF), and different h_FE distribution. The MPSH34 datasheet references the MPSH11 for comparative characterization only - direct substitution may alter gain, stability, or bias point, so circuit re-characterization is required before using MPSH34 as an MPSH11 replacement.