Signal
Voltage Comparator
Convert analog voltage to digital logic level.
What is it?
A comparator compares two analog input voltages and outputs a logic high or low depending on which is larger. Unlike an op-amp (which has feedback for linear operation), a comparator runs open-loop and is optimised for fast switching with sharp edges. Used as the boundary between analog and digital — threshold detectors, supply monitors, zero-crossing detectors, etc.
When do you need it?
- Power-supply over/under-voltage threshold detection.
- Reset / low-power wake supervisor circuits.
- Zero-crossing detection for AC mains (phase control).
- Window detection (two comparators feeding an AND).
- Schmitt-trigger conditioning of noisy analog inputs with hysteresis.
- Simple A/D conversion (e.g., flash ADC, ramp ADC building block).
How to pick the right one
- Number of channels
- Single (1G), dual (2G — most common, e.g. LM2903), quad (LM2901).
- Output type
- Open-collector / open-drain (needs pull-up, can wire-OR) or push-pull (faster edges, simpler).
- Supply range
- Single-supply 2-5.5 V for portable; wide single 2-36 V for industrial; dual-supply ±15 V for analog.
- Iq (quiescent current)
- <1 μA for always-on supervisors; 100-500 μA for general-purpose.
- Input common-mode range
- Does it include ground? Critical for single-supply use with ground-referenced signals.
- Propagation delay
- 100 ns for low-power; sub-10 ns for fast / RF applications.
What Magnias offers
Magnias comparator family includes the classic dual MVC2903A-TF2 (LM2903 class, AEC-Q100), the low-voltage dual MVC1362-AC (push-pull, 1.2-5.5 V), and the ultra-low-power MVC152 series (single, 210 nA quiescent, 0.85-5.5 V, rail-to-rail input, push-pull output).
Common questions
Why not use an op-amp as a comparator?
Op-amps without internal hysteresis or output rail-to-rail drive aren't optimised for switching. They can oscillate near the threshold and have slow recovery from saturation. Use a dedicated comparator for digital outputs.
Open-drain or push-pull?
Open-drain to wire-OR multiple comparator outputs (common in supervisors). Push-pull when you drive a single CMOS input directly — faster, cleaner.
What's hysteresis and how much do I need?
Adding a small positive feedback shifts the threshold depending on output state, preventing chattering on noisy inputs. 5-100 mV typical, scaled to the signal's noise amplitude.
MVC152 vs MVC1362-AC — which one for which job?
MVC152: single-channel, ultra-low-power supervisor — wake-up monitors, threshold detectors in battery designs. MVC1362-AC: dual-channel, push-pull, fast — supply supervisors needing both rails.