onsemi KSK595HMTF

Overview

KSK595HMTF from ON Semiconductor (formerly Fairchild) is a silicon N-channel junction field-effect transistor (JFET) optimized for low-noise, high-impedance audio preamplification in capacitor microphone circuits. It delivers IDSS = 150–350 µA, VGS(off) = –0.6 to –1.5 V, and forward transfer admittance |yfs| = 0.4–1.2 mS at VDS = 5 V, enabling stable biasing and minimal signal distortion in electret mic front-ends.

For engineers reviewing the KSK595HMTF datasheet, pinout, applications, or equivalent options, key selection criteria include gate-source cutoff voltage tolerance, drain current consistency at zero gate bias, input capacitance (< 3.5 pF), and SOT-23 thermal derating behavior under continuous 100 mW dissipation limits.

Technical Context

The KSK595HMTF operates as a depletion-mode JFET with fixed-channel conduction at VGS = 0 V, requiring negative gate bias to pinch off. Its low Crss (0.65 pF typ.) and Ciss (3.5 pF typ.) minimize Miller effect in high-gain AC-coupled microphone amplifiers.

Designed for DC-coupled source-follower configurations, it supports stable operation across –55°C to +150°C storage and up to +150°C junction temperature, with guaranteed BVGDO = –20 V and IG ≤ 10 mA absolute maximum ratings.

Key Specifications

Pinout & Package

SOT-23 surface-mount package with gull-wing leads; 1.3 mm × 2.9 mm footprint, 1.0 mm height, and thermal pad not present. Standard JEDEC MO-178 variant.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar JFET microphone biasing applications.

Compared with MMBFJ113 and 2N5484, the KSK595HMTF offers narrower VGS(off) distribution and lower input capacitance-critical for consistent sensitivity and extended high-frequency response in space-constrained electret mic modules.

Availability

KSK595HMTF is available at Aetrix Electronics and suitable for electret microphone biasing, low-noise audio preamplification, and telephone handset front-end design requiring stable component supply across industrial and consumer production cycles.

Supply support for KSK595HMTF 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 (acquired Fairchild Semiconductor in 2016) designs high-performance analog, discrete, and power management semiconductors for automotive, industrial, and communications markets.

The KSK595HMTF belongs to Fairchild's legacy low-noise JFET product line, specifically engineered for capacitor microphone applications demanding high input impedance, low capacitance, and stable DC operating points.

FAQ

What is the maximum gate-drain voltage rating for KSK595HMTF?

The KSK595HMTF has an absolute maximum gate-drain voltage (VGDO) of –20 V, measured at Ta = 25°C. This rating applies under reverse-biased conditions and must not be exceeded during ESD events, power-up sequencing, or transient surges. Operation beyond this limit risks irreversible gate oxide damage. The KSK595HMTF datasheet specifies BVGDO = –20 V at IG = –100 µA, confirming its robustness in typical microphone bias circuits where gate is held near ground potential.

Does KSK595HMTF require external bias resistors in electret microphone applications?

Yes, the KSK595HMTF requires external biasing: a drain load resistor (typically 2–10 kΩ) and gate-to-source resistor (≥ 1 GΩ) to establish proper DC operating point. Because it is a depletion-mode JFET, it conducts at VGS = 0 V; the gate resistor provides DC return path while preserving high input impedance. The KSK595HMTF's specified IDSS and VGS(off) ranges guide resistor selection to achieve target drain current and gain-no internal bias circuitry is integrated.

What is the typical input capacitance of KSK595HMTF and how does it affect audio performance?

The KSK595HMTF exhibits a typical input capacitance (Ciss) of 3.5 pF at VDS = 5 V and f = 1 MHz. This low value minimizes high-frequency attenuation and phase shift in electret microphone interfaces, supporting full-bandwidth audio capture up to 20 kHz and beyond. When used with standard 2.2 kΩ load resistors, the RC time constant remains well below audible thresholds. The KSK595HMTF's Ciss directly contributes to its suitability in compact, high-fidelity voice input stages where stray capacitance must be tightly controlled.

Can KSK595HMTF be used in place of KSK596HMTF?

No-KSK595HMTF and KSK596HMTF are distinct parts with non-interchangeable specifications. The KSK596HMTF has higher IDSS (300–800 µA) and more negative VGS(off) (–1.0 to –2.5 V), resulting in different bias points and gain characteristics. Substituting KSK595HMTF for KSK596HMTF would alter quiescent current, output impedance, and frequency response. The KSK595HMTF datasheet does not list KSK596HMTF as a drop-in replacement, and no pin-compatible equivalence is documented.

Is KSK595HMTF RoHS compliant and lead-free?

Yes, KSK595HMTF is RoHS compliant and lead-free. As a Fairchild product manufactured post-2006 and currently distributed by ON Semiconductor, it meets EU Directive 2011/65/EU requirements. The SOT-23 package uses matte tin (Sn) lead finish, and all homogeneous materials pass Pb < 1000 ppm threshold. The KSK595HMTF part marking, packaging, and certification documentation confirm full compliance-no exemptions apply.