P5.3-1 The inputs to the circuit shown in Figure P5.3-1 are the voltage source voltages v1 and v2.. The output of the circuit is the voltage vo. The output is related to the inputs by

vo = a v1 + b v2

where a and b are constants. Determine the values of a and b.

p5_3_17

Figure P 5.3-1

 

We use superposition, so shutting off a voltage source means replace the voltage source with a short circuit.  When we consider the effect of only v1, the circuit looks like

is the voltage across the 20 resistor.  The 20 is in parallel with the 5 resistor

 

 

So the circuit looks like

Use voltage division

 

Now deactivate and the circuit becomes

This time the two 20 Ω resistors are in parallel so the effective resistance is

 

 

So the circuit is

Again use voltage division

 

 

So adding these two results we have

 

 

So comparing with

Gives

 

 

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This page last updated on February 17, 2019