OPERATIONAL AMPLIFIERAn operational Amplifier is a direct Coupled high gainamplifier usually consisting of one or more differentialamplifiers and usually followed by a level translator and outputstage.The Operational Amplifier is a versatile device that can beused to amplify dc as well as input signal and was originallydesigned for computing such mathematical functions asAddition, Subtraction, Multiplication and Integration etc.33- input+ input-++ Vss- VssOutput
CIRCUIT DIAGRAM OF Op-Amp44
INVERTING & NON-INVERTING OP-AMPLIFIERVout = - Vin(Rf/Rin) Vout = Vin(1+Rf/Rin)INVERTING NON-INVERTING55In this circuit the input signal isamplified by gain A and also inverted.In this circuit the input signal isamplified by gain A and is in phase withinput signal.
66BUFFERDigital Buffer is nothing a but Even numbers of NOT gates cascade Connected.I/P O/P(Same as Input)Invert of I/PIdeal buffer has a properties :perfect linearity, regardless of signal amplitudes; and instantoutput response, regardless of the speed of the input signalBuffer is device which gives o/p as what ever input is given to it.
BUFFER OP-AMPLIFIER77signal input -++ VssSignal Out- VssThe op-amp configuration shown at left is a voltage-follower often used as abuffer amplifierOutput is connected directly to negative input (negative feedback)Since v+ = v- = vIN, and vOUT = v-, we can see by inspection that theclosed-loop gain Ao = 1We can obtain the same result by writingvOUT = A (vIN – vOUT) orvOUT/vIN = A/(1 + A) = 1 for A >> 1
888• This is a special case of the non-inverting amplifier, which is also called a voltage follower,(Voltage Series Feed Back Amplifier)with infinite R1 and zero R2.Hence Av = 1.• It provides an excellent electrical isolation while maintaining the signal voltage level.• The “ideal” buffer requires no input current and can drive any desired load resistancewithout loss of signal voltage.• Such a buffer is used in many sensor and data acquisition system applications.• Used as a "line driver" that transforms a high input impedance (resistance) to a low outputimpedance. Can provide substantial current gain.BUFFER OP-AMPLIFIERAHigh outputimpedanceBLow inputimpedance
990inOOis VAIRIRV:KVL0inOO VAIRoutV-:KVLIRV iin:VARIABLEGCONTROLLINiOOisoutRARRVV11SOLVING1SoutOVVACIRCUIT AND MODEL FOR UNITY GAIN BUFFER
1010TRANSFER CURVEA typical voltage-follower transfer curve is shown for VPOS = +15V andVNEG = -10VFor vIN between –10 and +15 volts, vOUT = vINIf vIN exceeds +15V, the output saturates at VPOSIf vIN < -10V, the output saturates at VNEGSince input current is zero giving zero input power, the voltage follower canprovide a large power gain.