Pitt MEMS 1082 - Mechatronics (27 pages)

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Mechatronics



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Mechatronics

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Pages:
27
School:
University of Pittsburgh
Course:
Mems 1082 - ELECTROMECHANICAL SENSORS AND ACTUATORS

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MEMS1082 Mechatronics Chapter 5 4 Operational amplifier Instrumentation amplifier Very high input impedance Large common mode rejection ratio CMRR Capability to amplify low level signals Consistent bandwidth Integrator Lossless capacitor 1 RC VO yt 1 RC t o x t dt t o vin dt t k x t dt o Differentiation and integration VO 1 RC t o vin dt Improved Integrator Lossy capacitor Rs is shunt resistor Rs 10R1 The use of shunt resistor is to limit the low frequency gain of the circuit Otherwise a small DC offset at the input would be integrated over time eventually saturating the op amp DC offset due to the input bias current can be minimized by R2 Choose R2 R1 Rs R1 Rs Integrator Example vs 15e vo 0 2t ut V 10 V Find vo t for t 0 Summing Integrator ic t vc t vc t i1 t 1 C 1 C i2 t t o t 0 v1 t R1 v2 t R2 x1 t R1 ic t dt v1 t R1 v2 t dt R2 yt yt x2 t R2 t 0 t 0 x1 t R1C k1 x1 t x2 t dt R2C k2 x2 t dt Differentiator Differentiator The input signal to the differentiator is applied to the capacitor The capacitor blocks any DC content so there is no current flow to the amplifier summing point resulting in zero output voltage The capacitor only allows AC type input voltage changes to pass through and whose frequency is dependant on the rate of change of the input signal At low frequencies the reactance of the capacitor is High resulting in a low gain Rf Xc and low output voltage from the op amp At higher frequencies the reactance of the capacitor is much lower resulting in a higher gain and higher output voltage from the differentiator amplifier Differentiator Improved Differentiator Amplifier Example Integrator and Switch An integrator and a voltage controlled switch An integrator is a circuit that can perform the mathematical operation of integration The output voltage vo t is related the input of the integrator vs t v0 t K t2 t1 vs t dt vo t1 Integrators have many applications One is to measure a time interval t2 t1 v 0 t2 K t 2 t1 Vs vo t1 Example Integrator and Switch



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