# Stability Circles MCQ’s

This set of RF & Microwave Circuit Design Multiple Choice Questions & Answers (MCQs) focuses on “Stability Circles”.

1. ____________ condition, if met then the transistor can be impedance matched for any load.
a) Conditional stability
b) Unconditional stability
c) Infinite gain
d) Infinite input impedance

2. A network is said to be conditionally stable if:
a) │Гin│<1, │Гout│<1.
b) │Гin│>1, │Гout│>1
c) │Гin│>1, │Гout│<1
d) │Гin│<1, │Гout│>1

3. For a transistor amplifier to be stable, either the input or the output impedance must have a real negative part.
a) True
b) False

4. Stability condition of an amplifier is frequency independent and hence can be operated at any frequency.
a) True
b) False

5. If │S11│>1 or │S22│>1, the amplifier cannot be unconditionally stable.
a) True
b) False

6. The condition for unconditional stability of a transistor as per the K-∆ test is │∆│> 1 and K<1.
a) True
b) False

7. For a unilateral device condition for unconditional stability in terms of S parameters is:
a) │S11│<1, │S22│<1
b) │S11│>1, │S22│>1
c) │S11│>1, │S22│<1
d) │S11│<1, │S22│>1

8. For any passive source termination ГS, Unconditional stability implies that:
a) │Гout│<1
b) │Гout│>1
c) │Гin│<1
d) │Гin│>1

9. If the S parameters of a transistor given are
S11=-0.811-j0.311
S12= 0.0306+j0.0048
S21=2.06+j3.717
S22=-0.230-j0.4517
Then ∆ for the given transistor is:
a) 0.336
b) 0.383
c) 0.456
d) None of the mentioned

10. By performing the K-∆ test for a given transistor the values of K and ∆ were found to be equal to 0.383 and 0.334 respectively. The transistor with these parameters has unconditional stability.
a) True
b) False