Operational Amplifier Fundamentals Unit 7 – The Difference Amplifier
Exercise 1 – Difference Amplifier DC Operation
EXERCISE OBJECTIVE
When you have completed this exercise, you will be able to operate a difference amplifier using
dc voltages. You will verify your results with a multimeter.
EXERCISE DISCUSSION
- The difference amplifier circuit on the circuit board has resistors R1, R2, R4, and R5 equal to
each other. - Due to the resistor values, VO equals V2 - V1, or the difference between the input voltages.
- The output voltage polarity is determine by the relationship between the noninverting input
voltage (V2) to the inverting input voltage (V1). - The V2 polarity dominates the V1 polarity and determines the output voltage polarity.
- The following relationships apply (U1 is not saturated) to the difference amplifier circuit.
VO = VA - V1
VA = (V2 x R4)/(R2 + R4)
VD = 0V VA = VR4