ECEN 215, Principles of Electrical EngineeringDr. Mina RahimianLecture# 21 Date: 11/6/13A negative feed back keeps the opamp in the linear mode with Vp ≈ Vn. Without a negative feedback, with a few millivolts between Vp and Vn the opamp becomes saturated.ComparatorIntegrating amplifier circuitIf the feedback resistor in the inverting amplifier circuit is replaced by a capacitor, the output voltage will be proportional to the integral of the input signal. This circuit is called an integrator and used in numerous applications.Differentiator circuitIf the input resistor in the inverting amplifier circuit is replaced by a capacitor, the output voltage will be proportional to the differential of the input signal. This circuit is called a differentiator.Active filtersWe can design a low pass, high pass, band pass and band reject filters using opamps, resistors and capacitors. Active filters have several advantages over passive filters. They are capable of amplifying the signal as well as filtering. The amplication can be controlled.Low pass active filterHigh pass active filterGeneral solution for step and natural responses of RL and RC circuitsFor computing the step or natural response of RL and RC circuits follow these steps:1. Identify the variable of interest. Choose inductor current in an RL and capcitor voltage in an RC circuit.2. Determine the initial value of the variable using the circuit before switching when all inductors are short and capacitors are open at steady state.3. Determine the final vaule of the variable using the circuit after switching when all inductors are short and capacitors are open at steady state.4. Calculate the time constant by finding the equivalnt resistance connected to the inductor or capacitor in the circuit after switching. (Ƭ= L/R in an RL circuit and Ƭ = RC in an RC circuit)5. Use this general equation to find the expression for the variable:Review for exam 2Summary of natural and step response of RLC
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