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Bias Circuit

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Equation 12.4<br />

The 2 Vopeak is due to the fact that the integration is from minus Vopeak to plus Vopeak. The<br />

voltage drop across Ry has been neglected in the output.<br />

Suppose we choose Cf as the design parameter where Vs, T, Vopeak, and Ry (from Unit 11) are<br />

given. The capacitor is then selected according to<br />

Equation 12.5<br />

For example, for Vs = 1 mV, Vopeak = 5 V, Ry = 220 Ω and T = 1 mS (f = 1 kHz), Cf = 23 nF.<br />

In the integrator project, a sine-wave source is used. The integrated output for this case is<br />

Equation 12.6<br />

The sine term can be neglected and the resulting formulation can be used to predict the peak<br />

of the cosine for a given Cf and peak Vs.<br />

A more general solution for the output voltage for the noninverting integrator includes the<br />

current through the resistor Rf. If we neglect the voltage across Ry, (12.2) becomes, for this<br />

case (constant input or square-wave input)<br />

Equation 12.7<br />

The solution is<br />

Equation 12.8<br />

Replacing the exponential with the first three terms of an infinite series gives<br />

Equation 12.9

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