KA7809AE Linear Voltage Regulator IC Equivalent & Substitute Parts

Part Overview

The KA7809AE is a linear voltage regulator IC manufactured by onsemi, designed to provide a fixed positive 9V output at 1A current capacity in a TO-220-3 package. This device is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and component procurement. The KA7809AE serves applications requiring stable 9V regulation from input sources up to 35V with integrated over-temperature and short-circuit protection.

Key Parameters

Parameter	Value
Output Voltage (Fixed)	9V
Output Current	1A
Input Voltage (Max)	35V
Voltage Dropout (Max)	2V @ 1A (Typ)
Quiescent Current	6 mA
PSRR	58dB (120Hz)
Package	TO-220-3
Operating Temperature	0°C ~ 125°C
Protection Features	Over Temperature, Short Circuit

Substitute Part Grouping Explanation

Substitution of the KA7809AE is determined by the following critical parameters: fixed 9V output voltage, output current capacity, maximum input voltage rating, package type (TO-220-3), and protection features. Substitute parts are grouped into three categories based on output current capability:

Full Current Equivalents (1A Output): Parts with 1A output current matching the KA7809AE specification, including MC7809ACTG, MC7809CTG, MC7809BTG, and KA7809AETU. These provide direct functional replacement.

Higher Current Alternatives (1.5A to 2A Output): Parts with output current exceeding 1A, including L7809ABV-DG, L7809CV, and L78S09CV. These provide enhanced current capability while maintaining 9V output and TO-220-3 packaging.

Reduced Current Alternatives (500mA Output): Parts with 500mA output current, including MC78M09CTG and L78M09CV. These are suitable only for applications with reduced current requirements.

All substitute parts maintain the same 9V fixed output voltage, 35V maximum input voltage, TO-220-3 package configuration, and integrated protection features as the KA7809AE.

Parameter Comparison

Part Number	Manufacturer	Output Current	Quiescent Current (mA)	PSRR (120Hz)	Operating Temp	Product Status	RoHS Status
KA7809AE	onsemi	1A	6	58dB	0°C ~ 125°C	Obsolete	REACH Unaffected
MC7809ACTG	onsemi	1A	6	61dB	0°C ~ 125°C	Obsolete	ROHS3 Compliant
MC7809CTG	onsemi	1A	8	61dB	0°C ~ 125°C	Active	ROHS3 Compliant
MC78M09CTG	onsemi	500mA	—	80dB	0°C ~ 125°C	Obsolete	ROHS3 Compliant
L7809ABV-DG	STMicroelectronics	1.5A	6	61dB	-40°C ~ 125°C	Obsolete	ROHS3 Compliant
L7809CV	STMicroelectronics	1.5A	8	55dB	0°C ~ 125°C	Obsolete	ROHS3 Compliant
L78M09CV	STMicroelectronics	500mA	6	56dB	0°C ~ 125°C	Obsolete	ROHS3 Compliant
L78S09CV	STMicroelectronics	2A	8	47dB	0°C ~ 150°C	Obsolete	ROHS3 Compliant
MC7809BTG	onsemi	1A	8	61dB	-40°C ~ 125°C	Obsolete	ROHS3 Compliant
KA7809AETU	Fairchild Semiconductor	1A	6	58dB	0°C ~ 125°C	Active	ROHS3 Compliant

Engineering Selection Recommendations

For direct replacement of the KA7809AE with active product status and full compliance, MC7809CTG is the primary selection. This part maintains identical electrical specifications, operates at 1A output current, and carries ROHS3 compliance with active product status, ensuring long-term availability and supply chain stability.

KA7809AETU from Fairchild Semiconductor provides an alternative with active product status. This part matches the KA7809AE electrical characteristics exactly, including 6mA quiescent current and 58dB PSRR, and is available in bulk packaging.

For applications requiring extended temperature range operation, MC7809BTG extends the operating range to -40°C ~ 125°C while maintaining 1A output current and identical electrical performance.

For applications with higher current requirements, L7809ABV-DG and L7809CV provide 1.5A output capacity. L78S09CV extends this further to 2A output with operating temperature range to 150°C, suitable for demanding thermal environments.

For reduced current applications below 1A, MC78M09CTG and L78M09CV provide 500mA output with enhanced PSRR performance (80dB and 56dB respectively).

All substitute parts maintain TO-220-3 packaging, 9V fixed output, and integrated protection features. Selection should prioritize active product status for new designs and long-term component availability.

Frequently Asked Questions (FAQ)

Q: Can MC7809CTG directly replace KA7809AE in existing designs?

A: Yes. MC7809CTG provides direct functional replacement with identical 1A output current, 9V fixed output voltage, TO-220-3 package, and protection features. The primary difference is active product status, ensuring ongoing availability.

Q: What is the difference between 1A, 1.5A, and 2A output variants?

A: Output current rating determines maximum load current the regulator can supply. The KA7809AE is rated for 1A. Higher-rated parts (L7809ABV-DG at 1.5A, L78S09CV at 2A) can supply greater load current but are not required for applications drawing less than 1A. Lower-rated parts (MC78M09CTG at 500mA) are suitable only for applications with reduced current demands.

Q: Are all substitute parts available in TO-220-3 package?

A: Yes. All listed substitute parts use TO-220-3 package configuration, ensuring mechanical and thermal compatibility with the KA7809AE footprint.

Q: What does product status "Active" versus "Obsolete" mean for component selection?

A: Active products have ongoing manufacturing and supply chain support. Obsolete products have ceased production. For new designs, active products (MC7809CTG, KA7809AETU) are preferred to ensure long-term availability and support.

Q: Does quiescent current variation affect circuit performance?

A: Quiescent current (6mA to 8mA across variants) represents standby current draw. This variation is minor and does not affect regulator output voltage or load regulation performance. Selection based on quiescent current is appropriate only for ultra-low-power applications where standby current is critical.

Q: Can I use L78S09CV (2A) in place of KA7809AE (1A)?

A: Yes. Higher current-rated regulators are backward compatible with lower current applications. L78S09CV provides 2A capability, exceeding the 1A requirement, and maintains identical 9V output voltage and TO-220-3 packaging. This substitution is suitable when higher current capacity is beneficial or when L78S09CV availability is superior.

Q: What is PSRR and does it affect substitution decisions?

A: PSRR (Power Supply Rejection Ratio) measures the regulator's ability to reject input voltage ripple. The KA7809AE specifies 58dB at 120Hz. Substitute parts range from 47dB to 80dB. Higher PSRR values provide better noise rejection. For noise-sensitive applications, parts with higher PSRR (MC78M09CTG at 80dB) may be preferred, but standard applications are not affected by this variation.

Q: Are there temperature range considerations for substitution?

A: The KA7809AE operates 0°C ~ 125°C. MC7809BTG and L7809ABV-DG extend the lower limit to -40°C for cold environment applications. L78S09CV extends the upper limit to 150°C for high-temperature environments. Selection should match the application's actual operating temperature requirements.

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