onsemi KA7905

Overview

KA7905 from ON Semiconductor (formerly Fairchild) is a fixed-output, three-terminal negative voltage regulator delivering −5 V at up to 1 A output current. It features internal thermal overload protection, short-circuit protection, and safe operating area compensation. It is used in dual-rail power supplies, industrial control logic, and analog signal conditioning circuits requiring stable negative bias.

For engineers reviewing the KA7905 datasheet, pinout, applications, or equivalent options, key selection criteria include its −5 V output tolerance (±4%), dropout voltage of 2 V at 1 A, ripple rejection of 54–60 dB at 120 Hz, and TO-220 package thermal performance (R_θJA = 65°C/W).

Technical Context

The KA7905 operates as a monolithic series pass regulator with an internal PNP pass transistor, error amplifier, voltage reference, and protection circuitry. Its block diagram shows feedback from output to reference via resistive divider, enabling precise regulation independent of load or line variation within specified ranges.

It requires no external components for basic operation but benefits from input (2.2 μF solid tantalum) and output (1 μF) capacitors for stability and transient response. The device maintains regulation across 0°C to +125°C junction temperature and supports input voltages down to −35 V absolute maximum.

Key Specifications

Pinout & Package

KA7905 is housed in a standard TO-220 package (JEDEC variation AB), with the metal tab electrically connected to Pin 2 (Input). Mounting requires electrical isolation if chassis ground is not tied to input rail.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar negative voltage regulation applications.

Compared with LM7905CT and KA7905TU, the KA7905 offers identical regulation performance, protection, and thermal characteristics; LM7905CT is a second-source option with identical functionality, while KA7905TU is a packaging-suffixed variant of the same part, both validated for drop-in use in legacy and new designs.

Availability

KA7905 is available at Aetrix Electronics and suitable for industrial control power, analog signal conditioning, RS-232 transceiver bias, and legacy logic support requiring stable component supply and long-term BOM continuity.

Supply support for KA7905 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 industrial, automotive, and computing markets.

The KA7905 belongs to the KA79XX series of three-terminal negative regulators designed for cost-sensitive, high-reliability linear power supply applications where simplicity, robustness, and long-lifecycle support are critical.

FAQ

What is the maximum input voltage for KA7905?

The KA7905 has an absolute maximum input voltage of −35 V. Operation above this risks permanent damage. For reliable −5 V output at 1 A, input should be maintained between −7 V and −20 V per datasheet conditions; exceeding −25 V increases dropout-related regulation error and thermal stress.

Does KA7905 require external capacitors?

Yes - KA7905 requires a 2.2 μF solid tantalum capacitor on the input (CI) and a 1 μF capacitor on the output (CO) for stability and transient response. Aluminum electrolytic capacitors may be used only if capacitance is increased ≥10× to compensate for ESR, and a reverse-biased 1N4001 diode must be added from input to output if CO exceeds 10 μF.

Is KA7905 pin-compatible with LM7905?

Yes - KA7905 is fully pin-compatible with LM7905 in TO-220 packages: Pin 1 = GND, Pin 2 = Input, Pin 3 = Output. Both share identical electrical specifications, thermal ratings, and protection features, enabling direct substitution without PCB modification.

What is the dropout voltage of KA7905 at full load?

The dropout voltage of KA7905 is 2 V at 1 A and +25°C junction temperature. This means the input must be at least −7 V to guarantee −5 V output under full continuous load; at higher temperatures or lower loads, dropout decreases slightly but must be verified per thermal design.

Can KA7905 be used in a split-rail ±12 V supply?

No - KA7905 is a fixed −5 V regulator and cannot generate −12 V. For ±12 V, use KA7912 (−12 V) paired with KA7812 (+12 V). The KA7905 datasheet explicitly lists KA7912 and KA7915 as members of the same family, each with dedicated output voltages and input voltage ranges.