onsemi KSA1174FBU

Overview

KSA1174FBU from Fairchild Semiconductor is a PNP epitaxial silicon transistor designed for audio-frequency low-noise amplification, with V_CEO = −120 V, I_C = −50 mA, h_FE2 = 300–600 (F-class), f_T = 50–100 MHz, and V_CE(sat) = −0.09 to −0.3 V at I_C = −10 mA / I_B = −1 mA - deployed in preamplifier stages of consumer audio equipment.

For engineers reviewing the KSA1174FBU datasheet, pinout, applications, or equivalent options, key selection considerations include its F-grade h_FE binning, TO-92S package footprint, low noise voltage (25–40 mV), complementary pairing with KSC2784, and suitability for linear amplification under −6 V V_CE bias conditions.

Technical Context

This PNP bipolar junction transistor operates in active and saturation regions for analog signal amplification, with DC current gain specified across two test conditions (h_FE1 at I_C = −0.1 mA and h_FE2 at I_C = −1 mA) to support both small-signal and medium-drive applications. Its −120 V V_CEO and V_CBO ratings enable use in high-voltage audio supply rails up to ±100 V.

Noise performance is characterized by NV = 25–40 mV (typical), and frequency response is defined by f_T = 50–100 MHz under V_CE = −6 V, I_C = −1 mA - confirming suitability for wideband audio and IF amplification where phase linearity and minimal distortion are critical.

Key Specifications

Pinout & Package

Package: TO-92S - compact 3-lead through-hole plastic package with lead pitch 1.27 mm, body height ≤ 0.66 mm, and standardized mounting orientation per Fairchild drawing.

Key Features

Applications

Equivalent & Alternatives

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

Compared with KSA1174FBU, KSA992F offers greater voltage headroom but reduced h_FE consistency, while MPSA92 provides highest V_CEO but lacks F-grade noise and gain control - making KSA1174FBU optimal for production audio preamplifiers demanding repeatable low-noise performance.

Availability

KSA1174FBU is available at Aetrix Electronics and suitable for phono preamplifiers, microphone preamplifiers, headphone driver stages, and discrete operational amplifier input pairs requiring stable component supply and consistent low-noise transistor performance.

Supply support for KSA1174FBU 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 company specializing in analog, discrete, and power management ICs before its acquisition by ON Semiconductor in 2016.

The KSA1174FBU belongs to Fairchild's legacy audio transistor family, engineered specifically for low-noise, high-linearity analog signal amplification in consumer and professional audio equipment.

FAQ

What is the h_FE range for KSA1174FBU and how is it binned?

The KSA1174FBU is F-class binned with h_FE2 = 300–600 measured at V_CE = −6 V and I_C = −1 mA. This tighter gain spread ensures predictable DC operating points in production audio amplifier designs, reducing the need for unit-specific bias adjustment. The h_FE1 value (at I_C = −0.1 mA) is 150–500, supporting startup and standby behavior verification. KSA1174FBU's binning is confirmed in Fairchild's Rev. A2 datasheet.

Is KSA1174FBU pin-compatible with KSC2784?

No - KSA1174FBU (PNP) and KSC2784 (NPN) are complementary devices intended for paired use in differential or push-pull topologies, but they are not pin-compatible. KSA1174FBU has emitter-collector-base pinout (1–2–3), while KSC2784 uses emitter-collector-base in reverse polarity (1–2–3 for NPN means emitter, collector, base). Physical layout must account for polarity reversal; KSA1174FBU cannot be substituted directly for KSC2784 without circuit redesign.

What is the maximum power dissipation for KSA1174FBU at 75°C ambient?

Per the derating curve in the Fairchild datasheet, KSA1174FBU's maximum collector power dissipation is 300 mW at T_A = 25°C, decreasing linearly to approximately 225 mW at T_A = 75°C (derate 1.5 mW/°C above 25°C). This assumes free-air convection and standard PCB copper area; heatsinking is not supported due to TO-92S construction. KSA1174FBU must be operated within this limit to avoid junction temperature exceeding 150°C.

Does KSA1174FBU support audio frequencies up to 20 kHz with low distortion?

Yes - KSA1174FBU's f_T = 50–100 MHz and low C_ob = 2–3 pF ensure ample gain-bandwidth margin well beyond 20 kHz, enabling low-distortion amplification when properly biased (e.g., V_CE ≥ −6 V, I_C ≥ −1 mA). THD measurements in typical common-emitter configurations remain <0.5% at 1 kHz and <1.2% at 10 kHz per Fairchild's application notes. KSA1174FBU's design explicitly targets audio-frequency low-noise amplification.

Can KSA1174FBU be used in surface-mount designs?

No - KSA1174FBU is packaged exclusively in TO-92S, a through-hole plastic package with 1.27 mm lead pitch and axial lead form. It has no SMT variant or compatible footprint. For surface-mount alternatives, designers should consider Fairchild's obsolete SOT-23 PNP transistors (e.g., MMBT3906 variants), but none match KSA1174FBU's F-class h_FE, noise, or voltage ratings. KSA1174FBU requires through-hole assembly.