KCC Quizzes AQQ303 about the radius of a circle
1. Quote of the month: "When I die, I want to die like my grandfather who died peacefully in his sleep. Not screaming like all the passengers in his car" - Will Rogers
2. Quiz AQQ304 about finding the radius of a circle
Good luck, and try to be
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August Monthly Blog Quiz! Read the blog, take the quiz, and you could win a gift card
Important: Read the blog first . The quiz questions are all based on the content of the blog:
Stay in the loop and win! Read the blog Current Output Driving Industrial Loops , then take our quick five-question quiz for a chance to win a gift card
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New challenge is here! It's AQQ259 related to a tunable or adjustable amplifier:

The above circuit is a tunable or adjustable gain amplifier. The opamp used is
considered as ideal (i.e. infinite open loop gain, infinite input resistance and
zero output impedance).
Questions:
1. For given R1, R2 and P, at which wiper position α, Vout = 0 volt?
2. Versus Vin, what is the dynamic range of Vout?
Good luck! And try to be among the first ones!
P.S. Don't hesitate to spread those weekly quizzes to colleagues or friends (we need more participants)!
1. Vout =0, alpha = R2/R1+R2
2. alpha = 0, Vout = -Vin * R2/R1
alpha = 1, Vout = Vin
1. Vout is 0V at α = R2/(R1+R2)
2. at α = 0: Vout = -Vin * R2/R1
at α = 1: Vout = Vin * (1-(R2/R1))
...and of course, Vout is limited to +Ecc max. / -Ecc min.
1. alpha= R2/(R1+R2)
2. Vout can span from Vin to (-R2/R1) * Vin
You use the simple relations for an ideal inverting and not inverting opamp. On the non inverting input, you have the partition between (1-alpha)*P and alpha*P, so you end up in the relation Vout= ((-R2/R1) + (1+R2/R1)*alpha)) * Vin. From this relation you can get the answers.
1. R2/R1 = alpha/(1-alpha) => alpha = R2/(R2+R1)
2. Vout=-R2/R1*Vin ... Vin, but it is also limited by Ecc, I am not sure, what does it exactly mean.
Bingo ; you get it. Congratulations:
Thanks Roland! Agree with your answer 1. But are you sure about question 2? You probably made a typo in an equation when calculating Vout for alpha=1... May be you can recheck?