Question

An amplifier has a supply voltage ±15v. Compute its peak to peak output swing

(a) 36v

(b) 30v

(c) 26v

(d) 49v

This question was addressed to me in an internship interview.

This question is from Interpreting of Data Sheets topic in chapter Operational Amplifier Characteristics of Linear Integrated Circuits

Answer 1

The correct answer is (b) 30V.

For an operational amplifier with a supply voltage of ±15V, the peak-to-peak output swing can be calculated as follows:

Output Voltage Range:

- Maximum positive output: approximately +13V to +14.5V (limited by saturation voltage)

- Maximum negative output: approximately -13V to -14.5V (limited by saturation voltage)

Peak-to-Peak Swing Calculation:

Peak-to-peak swing = (Positive maximum) - (Negative maximum)

Peak-to-peak swing ≈ 30V

This assumes the op-amp can swing within 1-2V of the supply rails, which is typical for most operational amplifiers. The actual maximum output swing is slightly less than the full supply voltage range (2 × 15V = 30V) due to the saturation voltage limitations of the output stage.