onsemi KSA733OBU

Overview

KSA733OBU from ON Semiconductor is a PNP epitaxial silicon transistor designed for low-frequency amplification and switching applications, with collector-base voltage of –60 V, collector-emitter voltage of –50 V, and DC current gain (hFE) ranging 40–700 depending on classification grade. It features TO-92 package, 250 mW power dissipation, and complements the NPN KSC945 in push-pull configurations.

For engineers reviewing the KSA733OBU datasheet, pinout, applications, or equivalent options, key selection considerations include its PNP polarity, low-noise performance (6–20 dB NF at 1 MHz), fT up to 180 MHz, saturation voltage below –0.3 V at IC = –100 mA/IB = –10 mA, and suitability for audio preamplifiers, signal inversion stages, and discrete bias networks.

Technical Context

The KSA733OBU operates as a general-purpose PNP bipolar junction transistor optimized for linear amplification below 100 MHz, with base-emitter on voltage between –0.50 V and –0.80 V at IC = –1 mA. Its output capacitance is 2.8 pF at VCB = –10 V, supporting stable gain in low-speed analog circuits.

It exhibits defined hFE classification bands (R/O/Y/G/L), enabling precise DC biasing across production lots. The device is rated for junction temperatures up to 150°C and storage from –55°C to +150°C, confirming robustness in industrial ambient conditions.

Key Specifications

Pinout & Package

Package: TO-92, 3-lead through-hole plastic package with standard lead spacing and mechanical dimensions per Fairchild Rev. A2 (2002). Pin 1 = Emitter, Pin 2 = Base, Pin 3 = Collector.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BC557 and MPSA92, the KSA733OBU delivers balanced performance for low-noise, medium-voltage amplification with graded h_FE and proven complementarity to KSC945-making it preferable for audio and precision bias designs where noise, gain consistency, and pairing matter.

Availability

KSA733OBU is available at Aetrix Electronics and suitable for audio preamplifiers, discrete bias networks, and low-speed switching applications requiring stable component supply, consistent h_FE grading, and reliable PNP complementarity to KSC945.

Supply support for KSA733OBU 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, and sensing solutions for automotive, industrial, and consumer markets.

The KSA733OBU belongs to ON Semiconductor's legacy general-purpose bipolar transistor product line, originally developed by Fairchild Semiconductor for cost-sensitive, high-reliability linear and switching applications in audio, instrumentation, and power control systems.

FAQ

What is the pin configuration of the KSA733OBU?

The KSA733OBU uses a TO-92 package with standardized pinout: Pin 1 is Emitter, Pin 2 is Base, and Pin 3 is Collector. This arrangement is confirmed in the original Fairchild datasheet Rev. A2 and matches industry-standard PNP orientation for common-emitter amplifier layouts. Always verify orientation via physical marking (flat side facing viewer, leads down) before PCB placement.

Does the KSA733OBU have a direct drop-in replacement?

No verified pin-compatible or drop-in replacement exists for the KSA733OBU. While BC557 shares the same TO-92 footprint and pinout, its lower voltage ratings and ungraded h_FE make it unsuitable for designs relying on KSA733OBU's –60 V V_CBO or L-grade gain. Any substitution requires full electrical validation of bias, noise, and switching behavior in the target circuit.

What does the "O" suffix in KSA733OBU indicate?

The "O" in KSA733OBU denotes the h_FE classification grade per Fairchild's binning system: O-grade devices have h_FE = 70–140 at V_CE = –6 V and I_C = –1 mA. The "BU" suffix reflects ON Semiconductor's post-integration part numbering convention, replacing underscores with dashes while preserving functional identity.

Can the KSA733OBU be used in RF applications?

The KSA733OBU is not intended for RF signal amplification above 30 MHz. Although its f_T reaches 180 MHz under test conditions, its noise figure, Cob, and lack of RF-optimized packaging limit practical use to low-frequency analog circuits (<10 MHz). For RF front-ends, purpose-built RF transistors such as MMBT918 or BF199 are recommended instead of KSA733OBU.

How does the KSA733OBU compare to the KSC945 NPN transistor?

The KSA733OBU is explicitly designed as the PNP complement to the KSC945 NPN transistor, sharing matching voltage ratings (–50 V V_CEO/+50 V V_CEO), similar f_T, and compatible TO-92 packages. This pairing enables symmetrical push-pull output stages, differential amplifiers, and complementary bias networks-where KSA733OBU handles current sinking and KSC945 handles current sourcing.