Lecture28-Nonideal+Operational+Amplifier

Lecture28-Nonideal+Operational+Amplifier - ECE 3040:...

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ECE 3040 - Dr. Ying Zhang Georgia Tech ECE 3040: Microelectronic Circuits Lecture 28 Reading: Jaeger 12.1-12.4, Notes
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ECE 3040 - Dr. Ying Zhang Georgia Tech + V out - + V in - Model Recapture: Ideal Operational Amplifier + V out - + V in - Circuit Symbol R in = Infinity, Voltage Gain, A v =Infinity at all frequencies R out =0
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ECE 3040 - Dr. Ying Zhang Georgia Tech v in v out i in i 2 i - i + i out v - v + Recapture: Inverting Amplifier Finite voltage gain results from an infinite voltage gain amplifier with “negative feedback” (feedback that takes a fraction of the output voltage and mixes it back into the negative summation node). 1 2 in v R R v o = Overall circuit gain is finite, negative (for this feedback configuration) and set by the feedback resistor network. Input Resistance: 1 R i v R in in in = = Output Resistance: 0 i v t t = = out R
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ECE 3040 - Dr. Ying Zhang Georgia Tech Recapture: Non-Inverting Amplifier v in v out i 2 i - i in v - v + 1 2 1 2 1 - in - 2 1 1 1 , v v so, v that v requires ground virtual The R R v v A R R R v v v v so R R R v v in out v out in out out + = = + = = = = + = + = = = 0 in in in in v i v R case) inverting - Non for as circuit (Same 0 = out R Virtual Ground or “short”
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ECE 3040 - Dr. Ying Zhang Georgia Tech Recapture: Unity Gain Buffer or “Voltage Follower” 1 1 0 1 2 1 2 = + = = = = v out v A R R v v A R and R except amplifier inverting Non as Same = = = 0 in in in in v i v R case) inverting - Non for as circuit (Same 0 = out R Can be used to isolate a high impedance circuit from a low impedance circuit
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ECE 3040 - Dr. Ying Zhang Georgia Tech Recapture: Summing Amplifier v in,a v out i in,a v - v + v in,b v in,c i in,b i in,c i 2 + + = = + + = + + = c R R v b R R v a R R v v c R R v b R R v a R R v v c R v b R v a R v R v i i i i c in b in a in out c in b in a in out c in b in a in out c in b in a in 1 2 1 2 1 2 1 2 1 2 1 2 1 1 1 2 , , , , , , , , , , , , 2 Output is a scaled sum of inputs. Scaling can be controlled by ratios of resistors
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ECE 3040 - Dr. Ying Zhang Georgia Tech Recapture: Difference Amplifier v in,a v out v- v+ v in,b v- v+ v out v th v in,b 2 1 2 1 2 , || R R R and R R R v v th a in th = + = Using Superposition we can combine the results of the Inverting and Non-inverting solutions: 1 2 , 1 2 2 1 2 , 1 2 1 1 R R v v R R R R R v v R R v v a in out a in out th out = + + = + = 1 2 b in, v R R v out = () 1 2 b in, a in, 1 2 b in, 1 2 a in, v v v v R R v R R R R v out out = = v in,a =0 v in,b =0 This circuit amplifies the difference of two signals
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ECE 3040 - Dr. Ying Zhang Georgia Tech + - R2 R1 V in V out C2 At DC (s=0), the gain remains the same as before (-R 2 /R 1 ). At high frequency, R
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This note was uploaded on 09/05/2009 for the course ECE 3040 taught by Professor Hamblen during the Spring '07 term at Georgia Institute of Technology.

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Lecture28-Nonideal+Operational+Amplifier - ECE 3040:...

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