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Class Exercise 9 (May 17  22, 2004)
9. Opamp Converters with Parallel Negative Feedback Opamp Integrator Builder
So far, we have managed to derive, build and even "invent" a total of 68 circuit building blocks. Here, we will improve almost all passive circuits we have discussed on the first (1, 2, 3, 4, 5) converting them into almost ideal circuits with parallel negative feedback and putting them in the library ; thus it will grow with new 22 circuit building blocks reaching up to 90 basic circuits:
Opamp Resistive Circuits with Current Output  
voltagetocurrent converter  resistancetocurrent converter 
voltage controlled current source  resistance controlled current source 
voltage/resistance divider 
Opamp Resistive Circuits with Voltage Output  
currenttovoltage converter  resistancetovoltage converter 
current x resistance multiplier 
Opamp Compound Circuits with Voltage Input and Output  
inverting voltage divider  inverting voltage summer 
Opamp Reactive Circuits with Voltage/Current Output  
KINDS  integrators  differentiators 
I output  L integrator V > I  C differentiator V > I 
V output  C integrator I > V  L differentiator I > V 
Opamp Reactive Circuits with Voltage Input and Output  
KINDS  integrators  differentiators 
capacitive  RC integrator V > V  RL differentiator V > V 
inductive  LR integrator V > V  RL differentiator V > V 
Opamp Diode Circuits with Voltage Input and Output  
limiters  parallel  series 
functional  logarithmators  antilogarithmators 
9.1. Converting passive circuits into active ones (a universal principle). Deriving the idea of removing disturbance by antidisturbance from many situations of our life. Concretizing into a principle of removing voltage by antivoltage (parallel negative feedback).
9.1.1. Converting resistive passive circuits into opamp circuits.
9.1.1.1. Opamp converters with current output: voltagetocurrent converter, resistancetocurrent converter and voltageintoresistance divider. Keeping a constant current by supplementing the input voltage in order to compensate the losses in the load (method 3). Future application in ramp generators.
Example 1: How to make a current source? 

Example 2: How to make an ideal ammeter?  
9.1.1.2. Opamp converters with voltage output: currenttovoltage converter, resistancetovoltage converter and voltageintoresistance divider. 

The idea. 

The implementation. 
9.1.2. Converting reactive passive circuits into opamp circuits.
9.1.2.1. Capacitive circuits: integrators; differentiators. Application 1: ramp generation. Building ramp generator from an external square generator and an opamp RC integrator.
9.1.2.2. Inductive circuits: integrators; differentiators.
9.1.3. Converting imperfect diode circuits into opamp circuits: parallel diode limiter (an ideal diode), logarithmic and antilogarithmic converter.
9.2. Virtually decreasing a resistance and increasing a capacitance by parallel NFB. "Bottomless" capacitor (another view point at opamp RC integrator).
9.3. Transforming NFB opamp circuits into negative impedance circuits. Applications: negative impedance converters (NIC).
Last updated October 22, 2004
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