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Anglicky v odbornch pedmtech"Support of teaching technical subjects in EnglishTutorial: Mechanic - electrician

Topic: Electronics II. Class Operational Amplifiers: Comparators Part 1 - BasicsPrepared by: Ing. Jaroslav Bernkopf

Projekt Anglicky v odbornch pedmtech, CZ.1.07/1.3.09/04.0002je spolufinancovn Evropskm socilnm fondem a sttnm rozpotem esk republiky.

1A comparator is a device that compares two voltages.Its output indicates which of the input voltages is larger.Comparators Part 1 - BasicsOperational Amplifiers2Definition

VoutVi+Vi-

2If the voltage on the non-inverting input (Vi+) is higher than the other voltage (Vi-), the output voltage Vout is positive.And vice versa: If Vi+ is lower than Vi-, the output voltage Vout is negative. Comparators Part 1 - BasicsOperational Amplifiers3Description

VoutVi+Vi-

3Vout is positive, because Vi+ is higher than Vi-. Comparators Part 1 - BasicsOperational Amplifiers4Description

Vi-is higher than Vi+ thereforeVout is negative.

VoutVi+Vi-

4Comparators Part 1 - BasicsOperational Amplifiers5DescriptionOperational amplifiers as comparators disadvantagesOperational amplifiers are slow.Their output levels are not logic.

5Comparators Part 1 - BasicsOperational Amplifiers6Description

Operational amplifiers are slow.When a fast signal of a high frequency is applied to the inputs, an operational amplifier reacts too lazily.It needs a long time to wake up and then another long time to transit from one level to the other.

Vi-VoutVi+

6Comparators Part 1 - BasicsOperational Amplifiers7Description

Operational amplifiers are slow.The output Vout should start moving here when Vi+ becomes lower than Vi-.

But it starts more than 0.5s later here.

And stops moving another 2.5 s later here.

Vi-VoutVi+

7Comparators Part 1 - BasicsOperational Amplifiers8Description

The high level output voltage should have a TTL value, i.e. +5 V maximum. Here it is about +13.5 V.

The low level output voltage should be near to zero. Here it is about -13.5 V.

Vi-VoutVi+Output levels of operational amplifiers are not logic.

8Comparators Part 1 - BasicsOperational Amplifiers9Task

Vi+Vi-Vout = ???Complete the picture below. Suppose the extreme output voltages are 13.5 V.

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Comparators Part 1 - BasicsOperational Amplifiers10

Vi+Vi-Vout Solution

10Comparators Part 1 - BasicsOperational Amplifiers11Referenceshttp://www.wikipedia.comhttp://www.thefreedictionary.comhttp://holbert.faculty.asu.edu/eee202/EEE202_Lect8_OperationalAmplifiers.ppthttp://www.wisc-online.com/Objects/ViewObject.aspx?ID=SSE2803

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