In electronics, a comparator is a device which compares two voltages or currents and switches its output to indicate which is larger. More generally, the term is also used to refer to a device that compares two items of data. The field of electronics comprises the study and use of systems that operate by controlling the flow of electrons (or other charge carriers) in devices such as thermionic valves and semiconductors. ... now. ... In electricity, current refers to electric current, which is the flow of electric charge. ... In general, data consist of propositions that reflect reality. ...

A standard op-amp without negative feedback can be used as a comparator, as indicated in the following diagram. A 741 operational amplifier in a TO-5 metal can package An operational amplifier, often referred to as an op-amp, is a DC-coupled electronic differential voltage amplifier, usually of very high gain, with one inverting and one non-inverting input. ...

Image File history File links Op-amp_symbol. ...

When the non-inverting input (V+) is at a higher voltage than the inverting input (V-), the high gain of the op-amp causes it to output the most positive voltage it can. When the non-inverting input (V+) drops below the inverting input (V-), the op-amp outputs the most negative voltage it can. Since the output voltage is limited by the supply voltage, for an op-amp that uses a balanced, split supply, (powered by ± V_S) this action can be written:

V_out = V_S sgn(V₊ − V₋)

where sgn(x) is the signum function. Generally, the positive and negative supplies V_S will not match absolute value: Signum function In mathematics and especially in computer science, the sign function is a logical function which extracts the sign of a real number. ...

V_out <= V_S+ when (V₊ > V_-) else V_S- when (V₊ < V_-).

Equality of input values is very difficult to achieve in practice. The speed at which the change in output results from a change in input (often called the slew rate in operational amplifiers) is typically in the order of 10ns to 100ns, but can be as slow as a few tens of μs. In electronics, the slew rate is a nonlinear effect in amplifiers. ... An operational amplifier or op-amp is an electronic circuit module (normally built as an integrated circuit, but occasionally with discrete transistors or vacuum tubes) which has a non-inverting input (+), an inverting input (-) and one output. ...

A dedicated voltage comparator chip, such as the LM339, is designed to interface directly to digital logic (for example TTL or CMOS). The output is a binary state, and it is often used to interface real world signals to digital circuitry (see analog to digital converter). The LM339 accomplishes this with an open collector output. When the inverting input is higher, the output of the comparator is connected to the negative power supply. When the noninverting input is higher, the output is floating (has a very high impedance to ground). With a pull-up resistor and a 0 to +5V power supply, the output takes on the voltages 0 or +5 and can be interfaced to TTL logic: A Motorola 68000-based computer with various TTL chips. ... Static CMOS Inverter Complementary-symmetry/metal-oxide semiconductor (CMOS) (see-moss, IPA:), is a major class of integrated circuits. ... This article or section should include material from AD converters In electronics, an analog-to-digital converter (abbreviated ADC, A/D, or A to D) is a device that converts continuous signals to discrete digital numbers. ... This page is a candidate for speedy deletion, because: Non-informative cut-paste If you disagree with its speedy deletion, please explain why on its talk page or at Wikipedia:Speedy deletions. ... A pull-up resistor is used in the design of electronic logic circuits. ... A Motorola 68000-based computer with various TTL chips. ...

V_out <= V_cc when (V₊ > V_-) else 0.

A dedicated voltage comparator will generally be faster than a general-purpose op-amp pressed into service as a comparator. A dedicated voltage comparator may also contain additional features such as an accurate, internal voltage reference and adjustable hysteresis. A 741 operational amplifier in a TO-5 metal can package An operational amplifier, often referred to as an op-amp, is a DC-coupled electronic differential voltage amplifier, usually of very high gain, with one inverting and one non-inverting input. ... Hysteresis is a property of systems (usually physical systems) that do not instantly follow the forces applied to them, but react slowly, or do not return completely to their original state: that is, systems whose states depend on their immediate history. ...

It is incorrect to consider a comparator as a device with a differential (bipolar) input and a logic (0/V_cc) output as the inputs of real comparators are not isolated. This means that not only their difference affects the output but also their voltages must not exceed the power voltage range: V_S- ≤ V₊,V_- ≤ V_S+. In the case of TTL/CMOS logic output comparators negative inputs are not allowed: 0 ≤ V₊,V_- ≤ V_cc.

When comparing a noisy signal to a threshold, the comparator may switch rapidly from state to state as the signal crosses the threshold. If this is unwanted, a Schmitt trigger can be used to provide hysteresis and a cleaner output signal. In electronics, a Schmitt (or Schmidt) trigger is a comparator circuit that incorporates positive feedback. ... Hysteresis is a property of systems (usually physical systems) that do not instantly follow the forces applied to them, but react slowly, or do not return completely to their original state: that is, systems whose states depend on their immediate history. ...