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WHAT'S YOUR ENGINEERING QUOTIENT?

Problem 1—What is the current through the resistance Ro in the following circuit? What is this circuit known as?

In this circuit, the opamp functions as a non-inverting amplifier for Vx, so

V = 2 ý Vx

Also,

Io = I1 ý I2

Combining these two equations gives us:

Io = (Vin ý Vx)/R ý (Vx ý V)/R

= (Vin ý Vx)/R ý (Vx ý 2ýVx)/R

= (Vin ý Vx)/R ý (ýVx)/R

= Vin/R

Since the output current is independent of the actual value of Ro, this circuit is known as a voltage-to-current converter.

Note that this even works if Ro = 0, but then the opamp is not actually contributing to the operation of the circuit.

Contributor: Naveen P N

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