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Adjustable linear regulator

LM317 Internal Circuitry

Explore the internal circuitry and functional stages of LM317.

Package view

Inside LM317

A floating control loop inside the regulator package.

LM317 functional package cutaway with input, pass stage, output, reference, error amplifier and adjustment feedback.
Functional cutaway, not a physical silicon layout. The loop regulates OUTPUT relative to ADJUST.

Explore the circuit

Select a stage to see its role and connections

Floating reference

The reference controls OUTPUT minus ADJUST; there is no dedicated ground lead.

Pass-stage control

The error amplifier drives the series pass stage to keep the reference difference stable.

Protection

Current and thermal limiting protect the pass stage under abnormal conditions.

Component view