PowerWise® Design University

Operational Amplifier Applications

What is the likely cause of oscillation in op-amp circuits?
Too much or too/little feedback capacitance
Excessive capacitive load on the output
Oscillation of the power supply
All of the above

What are the reason(s) why the circuit below is only a theoretical circuit?
Stability Problems
Noise Problems
Thermal shut down
A and B

What characteristic(s) would be optimal for an ideal op-amp?
Infinite input impedance
Zero output impedance
Infinite gain
All of the above

Which Operational Amplifier Circuit has the highest impedance?
Summing Amp
Precision Current Source
Unity-Gain Buffer
Photodiode Amplifier

What is the best way to solve on op-amp oscillation problem?
Try fixing any one of these, and if that doesn't help, leave that fix on, and try another
Add a variable series-R-C damper from ground, to the output or input. Adjust the R and C values
Note the frequency of oscillation.
All of the above

What kind of theoretical operational amplifier circuit is shown below?
Differentiator
Low-pass Filter
Integrator
Non-Inverting

In the circuit below, when is it important to make R5=R1||R2||R3||R4?
When R5 is very large
When Ib is large
When R5 x Ib is large
When VS is large

How do you get R1/R2 = R3/R4?
Buy expensive resistors at 0.001%
Buy expensive matched resistors at 0.001%
Trim with POT
Place a capacitor between R3 and R4

How can you improve the noise and stability of this circuit?

Add a small amount of Cf in parallel with R1, Cf = 1/50 x C1
Add a large amount of Cf in parallel wth R1
Add a small amount of Rin in series with C1, about 1/20 x Rf
Both A and C