Understanding Ideal Op-Amp Circuits for Signal Processing
Explore the concepts of ideal op-amp circuits including adders, subtractors, differentiators, amplifiers, integrators, and more. Dive into inverting and non-inverting amplifier configurations, unity gain buffer, and the impact of finite open-loop gain on circuit performance. Gain insights into error percentages and gain calculations in op-amp circuits.
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Presentation Transcript
Lecture 11 September 15, 2023 1
Ideal OPAMP Adder, Subtractor, Differentiator, Amplifier, Integrator 2
Ideal OPAMP Differential inputs Single ended Output Infinite i/p resistance ??=0 ?0 + + _ Zero O/p resistance ??=0 ?? + _ ?? ?? Open loop gain Infinite ???? ?????? ???? ???? 3
Inverting Amplifier ???= 5V + ????= A?? ???=0V ?? + ???=-5V ???? ?? ??? 4
Non-Inverting Amplifier ???= 5V ????= A?? ???=0V + + ???=-5V ?? ???? ?? ??? 5
Follower and Inversion A C B C Follower A C Inversion B + 6
Unity Gain Buffer ????= ??(?? ??) ???= 5V + + ???? ????= ??(??? ????) ??? ???? ??? ?? = ???=-5V ?? 1 ???? ??? = 1 7
Inverting Amplifier ?2 Simplified Circuit ?2 ?2 ?2 ???= 5V ?1 ?1 ?? + + ???? ?1 ???? ?1 ??? ??? ?? + ????= ??(?? ??) ???? ?? ?? ??=0 ??= ?? Virtual short between ??and ?? ???= 5V = ?? ?? 8
Inverting Amplifier ?2 Simplified Circuit ?2 ?2 ?2 ???= 5V ?1 ?1 ?? + + ???? ?1 ???? ?1 ??? ??? ?? + ?? Virtual Grounded = 0 Hence ?1= ?2 ??? 0 ?1 ?2 ???? ??? ?1 ???= 5V =0 ???? =?2 Close Loop gain 9
Effect of finite Open loop Gain ????= ??(?? ??) ????= ????as ??is grounded ???? ?2 = ?? ?2 ?? ??? ?? ?1 =?? ???? ?2 ???= 5V ?1 + ???? ?? ?1 ???? ?? ?? ???+ ???? (Substituting ???? ???? ?1 = ??) = ??? ?2 ?? ?? ?2 ?1 + 1 +?2 Gain = ???? = ?????????: ?? ?1 1+(1+?2 ?1)1 ??? ?? ???= 5V ?2 ?1= - 40 If ?1= 500 and ?2= 20 k the Gain = 10
Percentage of Error ??= 1000 and ??= 106 ?2 ?1 ??? ??= 1000 ,???? = 38.424 Gain = 1+(1+?2 ?1)1 ??? ??= 106,???? = 39.998 ?? ???? ?2 ??? ??= 1000 ,?? = 3.94% ?1 Percentage of Error (PE) = x 100% ?2 ?1 ??? ??= 106, ?? = 0.004% If the ??= 106is 50% OFF then Gain = 39.996 11
Audio Mixer 12
OPAMP-Summing Amplifier ?1 ?1 ?? ?2 ?2 ?3 ?3 ?? ? ?? ?1+ ?2+ ?3+ + ??= ?? ?? ?? = (?? ?1+?? ?2+?? ?3+ +?? ??) ?1 ?1+ ?2 ?3 ?3+ + ?? ??= ?? ?? ?2+ ?1 ?2 ?3 ?? 13
OPAMP-Non Inverting Amplifier ?2 ?2 ????= ??(?? ??) ???= 5V ??= ??? ?1 ?1= ?2 ??? ???? ?1 ??? ?1 =???? ??? ?2 + + ??? ???= 5V ???? ??? = (1 +?2 ?1) What is the effect of finite open loop gain? 14
Differential Amplifier ????+??? 2 ??= ????+??? + ???? 2 Differential Amplifier ??= ???? ??? - 2 ???? ??? 2 ????= ?????+ ??????? Common mode Gain Differential Gain To define the quality of amplifier : Common Mode Rejection Ratio (CMRR)=20 log (|??| |???|) CMRR ideally infinite 15
OPAMP-Differential Amplifier (Subtractor) ?2 ?1 ??1 ??2 ?3 ?4 16
OPAMP-Differential Amplifier (Subtractor) ?2 ?2 ?2 ?2 ???= 5V ?1 ???= 5V ?1 ??? + ?? ???? ?1 ???? ?1 ??? ?? + + + ??? ???= 5V ???= 5V ???? ??? = ?2 ???? ??? = (1 +?2 ?1) ?1 17
OPAMP-Differential Amplifier (Subtractor) ?2 ?1 ??= ( ?2 ?1)??1+ (1 +?2 ?4 ?1)??2( ?3+ ?4) ??1 ??2 Conditions ?3 ?2 ?1 = (1 +?2 ?4 ?4 ?1) ( ?3+ ?4) ?2 ?1 =?4 ?3 ??=?2 (??2 ??1) ?1 18
