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Dual voltage comparator

LM2903 Working Principle

Learn how LM2903 works with an illustrated explanation and practical readings.

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LM2903 at a glance

Follow the labeled connections and functional stages

LM2903 working principle: illustrated functional stages, basic circuit and connections
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How it works

3 stages · Explore one step at a time

Step 1 / 3

Compare the two inputs

The differential input stage responds to IN+ minus IN−. No analog-to-digital converter or firmware is needed.

Step 2 / 3

Sink current or release the node

A negative input difference turns the output transistor on. A positive difference turns it off. The external pull-up supplies the HIGH level.

Step 3 / 3

Make a stable decision

Keep inputs in their common-mode range. Add positive-feedback hysteresis when a slowly changing or noisy signal would chatter around the threshold.

Find the switching threshold

Adjust VIN and the reference. Remove the pull-up to see why it matters.

5 V · DC explorer
IN+ − IN−—
Output state—
Pull-up current—

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05 V5 VSignal input voltage →Output voltage →

Violet: offset-sensitive transition · Amber: input outside the recommended range.

DC teaching model for channel A. The ±15 mV band uses the full-temperature maximum input-offset magnitude, not hysteresis or a complete error budget. LOW uses an illustrative 0.15 V estimate. Input bias, leakage, noise, timing and capacitance are omitted.

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