onsemi KA7809AE

Overview

KA7809AE from ON Semiconductor is a fixed-output, 3-terminal, 1 A positive linear voltage regulator delivering a nominal 9.0 V output with ±2% tolerance at +25°C and operating across 0°C to +125°C. It features thermal overload protection, short-circuit protection, and safe operating area (SOA) protection for robust operation in unregulated DC supply rails. It is commonly used in industrial power supplies, embedded control modules, and legacy analog instrumentation requiring stable low-noise 9 V bias.

For engineers reviewing the KA7809AE datasheet, pinout, applications, or equivalent options, key selection considerations include dropout voltage (2 V at 1 A), ripple rejection (62 dB at 120 Hz), output resistance (17 mΩ), load regulation (≤100 mV over 5 mA–1 A), and quiescent current (5–6 mA).

Technical Context

The KA7809AE implements a classic series-pass linear regulator architecture with internal error amplifier, reference voltage generator, current-limiting circuitry, thermal shutdown comparator, and SOA protection logic. Its feedback is internal and non-adjustable - output voltage is set by factory-trimmed resistive divider.

It operates under continuous conduction mode with no external compensation required. Input-to-output differential must remain ≥2 V for regulation; minimum input is 11.2 V at full load. Protection circuits activate independently: thermal shutdown triggers at ~150°C junction temperature, and short-circuit current is limited to ~250 mA during fault conditions.

Key Specifications

Pinout & Package

KA7809AE is supplied in TO-220 (dual-gauge) package with standard 3-pin configuration: Pin 1 = Input, Pin 2 = Ground, Pin 3 = Output. The metal tab is electrically connected to Pin 2 (GND) and serves as thermal path to heatsink.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar fixed-output linear regulator applications.

Compared with LM7809CT and MC7809BD2TR4, the KA7809AE offers tighter output tolerance and TO-220 through-hole compatibility while maintaining identical protection features and noise performance - making it optimal for legacy-replacement and industrial repair scenarios where mechanical fit and precision matter.

Availability

KA7809AE is available at Aetrix Electronics and suitable for industrial power supplies, embedded control modules, legacy analog instrumentation, and DC motor speed controllers requiring stable component supply, long-term lifecycle support, and drop-in replacement capability.

Supply support for KA7809AE 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 (formerly Fairchild Semiconductor) is a global semiconductor manufacturer specializing in power management, analog, and discrete devices for automotive, industrial, and cloud infrastructure markets.

The KA7809AE belongs to the KA78XXAE family of fixed-output linear regulators designed specifically for high-reliability industrial and legacy system replacement applications - emphasizing thermal robustness, wide-input tolerance, and long-lifecycle availability.

FAQ

What is the maximum input voltage for KA7809AE?

The absolute maximum input voltage for KA7809AE is 35 V, but the recommended operating range is 11.2 V to 24 V for reliable regulation at full 1 A load. Exceeding 24 V increases power dissipation and thermal stress - for inputs above 24 V, a pre-regulator or heat sink upgrade is required to maintain junction temperature within 0°C to +125°C limits. KA7809AE's dropout voltage remains 2 V across its operating range.

Does KA7809AE require external capacitors?

Yes, KA7809AE requires two external capacitors: a 0.33 μF ceramic capacitor between Input and GND (close to the device), and a 0.1 μF ceramic capacitor between Output and GND. These stabilize internal feedback and suppress high-frequency noise. Omitting either capacitor may cause oscillation or degraded ripple rejection. KA7809AE does not support electrolytic-only output capacitance due to ESR sensitivity.

How does KA7809AE handle short-circuit conditions?

KA7809AE limits short-circuit output current to approximately 250 mA at +25°C ambient, independent of input voltage (up to 35 V). This current limit is enforced by internal sensing and is active across the full temperature range. Simultaneously, thermal shutdown activates if junction temperature exceeds ~150°C - allowing automatic recovery once cooled. KA7809AE is not damaged by sustained short-circuit events under proper heatsinking.

Can KA7809AE be used in adjustable configurations?

No - KA7809AE is a fixed-output regulator with internal feedback network; it cannot be configured for adjustable output voltage. Unlike LM317 or KA78Lxx variants, it lacks ADJ pin or external resistor options. For adjustable 9 V+ outputs, consider using KA7809AE as pre-regulator feeding an ultra-low-noise LDO like NCP1117ST9T3G, or select a programmable switching regulator.

What is the thermal resistance of KA7809AE in TO-220 package?

KA7809AE in TO-220 (dual-gauge) package has R_θJC = 5°C/W (junction-to-case) and R_θJA = 65°C/W (junction-to-ambient, no heatsink). With a standard 1.5″×1.5″ 0.062″ copper heatsink, typical R_θSA is ~20°C/W, yielding ~25°C/W total thermal resistance. Derating is required above +70°C ambient: output current must be reduced linearly to 0 A at +125°C case temperature. KA7809AE's thermal shutdown threshold is ~150°C junction.