If the non-inverting input is lower than the inverting one then the output is high. Whilst it is easy to use an operational amplifier as a comparator, especially when it may be easy to use one if a chip containing multiple op amps has one spare. However it is not always advisable to adopt this approach. The op amp may not always function correctly, or it may not give the optimum performance.
That said, when the application is not demanding, it is always tempting to use these electronic components because they may already be available. Op amp latch-up: Under some conditions, especially when an op amp is being driven hard it is possible for it to latch up, i.
Comparators are designed to operate in this mode and should never latch up. Open loop operation: Operational amplifiers are designed to be used in a closed loop mode and their circuit is optimised for this type of scenario. Their operation is not characterised in open loop mode. Digital vs analogue: Operational amplifiers are essential analogue components and their internal circuitry is designed to operate in this region. Comparators are designed to be operated as a logic function, i.
This means that operational amplifiers are best when they are operating in an analogue mode with the output not hitting the rails, whereas comparators are not so good at operating in a linear mode, and are far better at operating with logic levels.
Output stages: The output stages of operational amplifiers and comparators are very different. Typically operational amplifiers have a linear output, often operating in a complementary symmetry fashion to give optimum linear performance for the output. Comparators often have an open collector output suitable for driving into digital interfaces. They are designed to interface with logic circuitry, providing a logic input from a comparison of analogue voltages.
Response times: Comparators are optimised to provide very fast response and switching times. Slew rates are fast and provide optimum performance. Operational amplifiers are not optimised for these characteristics. They tend to be much slower electronic components optimised for linear operation rather than speed.
This is required for good switching of logic circuits. Op amps will not be able to drive hard to the rails as they have a certain saturation voltage - this may lead to poor switching of logic circuits. In view of these factors, it is always preferable to utilise a comparator chip where this type of operation is envisaged. It is possible to use an op amp as a comparator as it fulfils the basic requirements for the function.
In operation the operational amplifier goes into positive or negative saturation dependent upon the input voltages. As the gain of the operational amplifier will generally exceed the output will run into saturation when the inputs are only fractions of a millivolt apart. Although op amps are widely used as comparator, special comparator chips are far better. These specific comparator chips offer very fast switching times, well above those offered by most op-amps that are intended for more linear applications.
As a result the comparator output voltage switches between the upper and lower saturation levels. To reduce further offset problems, offset voltage compensating networks and offset minimizing resistors can be used.
Hi I would like to build voltage amplifier as well as regulator using lm The input would be 50 mv to 50 volt. The input pulses per min would be The output pulse should be regulated 5 volt at all frequencies and voltage inputs. Plz if you could build the schematics for me. The clamp diodes D1, D2 are useless. R1, R are useless as well. There is nothing to protect about inputs.
D1 and D2 are for protesting the input stage of the Comparator IC. R to take care of input impedance to take care of offset voltage R1 to set the threshold voltage for triggering the output. Please go through a good text book on operational amplifiers. It helps me to know more about the op-amp in the form of comparators.
Author jojo. Dear 6 years ago. Mihai 7 years ago. It is very useful. Let us draw the output wave form of an inverting comparator, when a sinusoidal input signal and a reference voltage of zero volts are applied to its inverting and non-inverting terminals respectively. During the positive half cycle of the sinusoidal input signal, the voltage present at the inverting terminal of op-amp is greater than zero volts.
Similarly, during the negative half cycle of the sinusoidal input signal, the voltage present at the inverting terminal of the op-amp is less than zero volts. The following figure shows the input and output waveforms of an inverting comparator, when the reference voltage is zero volts. In other words, output changes its value when the input is crossing zero volts.
Hence, the above circuit is also called as inverting zero crossing detector. A non-inverting comparator is an op-amp based comparator for which a reference voltage is applied to its inverting terminal and the input voltage is applied to its non-inverting terminal. This op-amp based comparator is called as non-inverting comparator because the input voltage, which has to be compared is applied to the non-inverting terminal of the op-amp. The operation of a non-inverting comparator is very simple.
Let us draw the output wave form of a non-inverting comparator, when a sinusoidal input signal and reference voltage of zero volts are applied to the non-inverting and inverting terminals of the op-amp respectively.
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