KCC's Quiz AQQ259 about a tunable gain amplifier

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. 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.

For the dynamic range answer, you also need to take into account Ecc and -Ecc value.

Indeed, Vout cannot exceeds Ecc and -Ecc

Thanks Gaetano! All answers are correct, congratulations!

What happened to P in your equation? I got the same result, but I have it as:
((-R2/R1) + (1+R2/R1)*alpha*P)) * Vin

Could you please advise?

Thanks BOZC ! In fact you have just made a little mistake in the non-inverting part of the gain: the portion of Vin introduced by the potentiometer is just alpha*Vin and not alpha*P*Vin...