Operational Amplifier Voltage Comparator Circuits

Posted on Feb 6, 2014

A voltage comparator is a device that compares the voltage at the two inputs and develops an output based on the inputs. A high output when the plus input is greater than the minus input or a low output when the plus input is less than the minus input. A comparator is a component that compares the two analog inputs and outputs a digital signal tha

Operational Amplifier Voltage Comparator Circuits
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t represents which input signal is greater than the other. An acceptable analog input depends on the actual voltage comparator used and the voltage used to power it. The digital output can be almost any digital signal and again depends on the comparator and the voltage used to power it. However; the outputs might include an Open Drain, Open Collector, TTL Totem Pole, LVDS, or Push-Pull, to list the most common. So even though the input is analog, the output could directly interface with many of the TTL logic families. Although the voltage comparator is not an operational amplifier, an application might still use the terms inverting and non-inverting. An inverting voltage comparator would apply a signal to the minus input while the plus terminal is fixed to a voltage reference. The non-inverting voltage comparator would apply the signal to the plus input while the minus terminal is fixed to a voltage reference. So the terms apply to an input being above a reference and than having the output switch either high [non-inverting] or low [inverting]. A zero crossing detector may be produced by applying the input to the plus terminal and grounding the minus terminal. The output goes high when the input goes above the ground reference. Hysteresis may be added to a voltage comparator by applying feedback. The configuration begins to appear like an operational amplifier circuit, but the circuit is still a comparator and will never...

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