OPAMPS APPLICATIONS OF INVERTING OPAMP II Prepared by
OP-AMPS: APPLICATIONS OF INVERTING OPAMP : II � Prepared by: 1331_005 for Collaborative Creation of OER � Target Audience: 2 nd year; 3 rd semester Engineering Students
INTEGRATOR
v v So far, the input and feedback components have been resistors If the feedback component used is a capacitor, as shown in Fig. a, v the resulting connection is called an integrator.
v v v The virtual-ground equivalent circuit (Fig. b) shows that v an expression for the voltage between input and output v can be derived in terms of the current I, from input to output. Recall that virtual ground means that we can consider the voltage at the junction of R and XC to be ground (since Vi = 0 V) but that no current goes into ground at that point. The capacitive impedance can be expressed as where s = j
v Solving for Vo/V 1 yields v The expression above can be rewritten in the time domain as v A circuit in which the output voltage waveform is the integral of the input voltage waveform is called integrator.
v v Last Equation in previous slide shows that v the output is the integral of the input, v with an inversion and scale multiplier of 1/RC. The ability to integrate a given signal provides v the analog computer with the ability to solve differential equations and v therefore provides the ability to electrically solve analogs of physical system operation. The integration operation is one of summation, summing the area under a waveform or curve over a period of time.
v v If a fixed voltage is applied as input to an integrator circuit, vlast Eq. shows that the output voltage grows over a period of time, vproviding a ramp voltage. Equation can thus be understood to show that v the output voltage ramp (for a fixed input voltage) is opposite in polarity to the input voltage and v is multiplied by the factor 1/RC.
Example: Consider an input voltage, V 1 = 1 V, to the integrator circuit. The scale factor of 1/RC is
v v v so that the output is a negative ramp voltage as shown in Fig. b. If the scale factor is changed by making R 100 k , for example, then and the output is then a steeper ramp voltage, as shown in Fig c.
DIFFERENTIATOR
v v A circuit in which the output voltage waveform is the differentiation of input voltage is called differentiator The differentiator does provide a useful operation, the resulting relation for the circuit being where the scale factor is -RC.
v v The input signal will be differentiated properly vif the time period T of the input signal is larger than or equal to Rf. C As the frequency changes, the gain changes. Also, at higher frequencies the circuit is highly susceptible at high frequency noise and noise gets amplified. Both the (high frequency noise and gain reduction) problem can be corrected by v adding, few components.
REFERENCES “Operational Amplifier Basics” 1. www. electronic-tutorials. ws/opamp_1. html 2. Electronic Devices and Circuit Theory”, Nashelesky & Boylestead, PHI.
THANK YOU
- Slides: 14