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Summing amplifier

Inverting amplifier configuration may be used to perform several mathematical operations. The summing amplifier provides an output related to the algebraic sum of two or more signals.
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Wire up a summing amplifier, as shown.
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Plot $V_{\rm out}$ vs. $V_2$ for constant $V_1$, and $V_{\rm out}$ vs. $V_1$ for constant $V_2$. Explain the values of the slopes and intercepts.

Disconnect the summing network from the 351; leave the balance pot and power connections in place for later use.

Design a circuit whose output represents $3V_{1}-4V_{2}$.

Design and describe an inverting amplifier with a thermistor as one resistor such that the output voltage becomes more positive as the temperature inreases. The thermistor resistance is 10.5 k$\Omega$ at 28$^\circ$C and 9.5 k$\Omega$ at 23$^\circ$C. Choose the component values so that $V_{\rm out}$ changes 10 mV per $^\circ$C near room temperature. Also include an offset circuit so that $V_{\rm out} = 250$ mV at $25^\circ$C. Assume that the thermistor resistance changes linearly with $T^{-1}$.



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Last revised: 2007-01-05