All RF Cafe quizzes would make perfect fodder for employment interviews for technicians or engineers
- particularly those who are fresh out of school or are relatively new to the work world. Come to
think of it, they would make equally excellent study material for the same persons who are going to
be interviewed for a job.Some of these books used in quizzes
are available as prizes in the monthly
RF Cafe Giveaway
Note: Many answers contain passages quoted from the text.
Return to RF Cafe Quiz #49
quiz is based on the information presented in
High-Frequency Integrated Circuits, by Rosin Voinigescu.
Cambridge University Press graciously provided this book.
Note: Some of these books are available as prizes in the monthly
RF Cafe Giveaway.
1. Why are S-parameters preferred for high frequency network analysis?
b) Open and short circuit terminations are not required
True open and short circuit terminations,
which are required for Y-, Z-, h-, and G-parameters, are difficult to achieve at high frequencies, but S-parameters
use easily produced impedance values such as the standard 50 Ω and 75 Ω. (see page 82)
2. To what temperature is noise figure normally referenced?
Friis suggested that the noise figure (factor) be defined wrt a reference temperature of 290 K.
(see page 107)
3. Where does the Quantum Confinement (QC) effect occur
in a MOSFET?
b) At the gate
QC occurs in the quasi-triangular potential well formed in the inversion
layer at the channel-gate dielectric interface. (see page 176)
Why is substrate resistance important?
d) It degrades fMAX and FMIN
substrate resistance is important in high-frequency and high-speed applications because it degrades fMAX
and FMIN. (see page 191)
5. At what rate has MOSFET gate
shrink scaling factor (√2) occurred since the 1970s?
b) Every 2-3 years
Ever since the
first commercial LSI CMOS circuits appeared in the early 1970s, the minimum feature size ofCMOS technology, usually
represented by the physical gate length of the MOSFET, has shrunk by a factor S = √2 every 2-3 years.
(see page 209)
6. Who developed the first High Electron Mobility Transistor
c) Fujitsu (Japan)
The first HEMT was fabricated by Fujitsu, in Japan, in 1980.
(see page 254)
7. When is coplanar waveguide (CPW) more desirable than
microstrip on a semiconductor substrate?
c) When a ground plane located on the top of the IC is not
In situations where a ground plane on top of the semiconductor wafer is not feasible or has high
loss, CPW can have (significantly) lower loss than microstrip lines realized directly over the silicon substrate.
(see page 301)
8. What is the definition of Power Added Efficiency (PAE)
of a power amplifier?
d) (POUT - PIN) / PDC
PAE is the ratio
of the difference in input and output signal power and the DC supply input power. (see page 375)
9. What is the best type of biasing for an Low Noise Amplifier (LNA) at high
d) Complimentary to Absolute Temperature (CTAT) current mirror bias
Peak gain current
density does not change with temperature; therefore, PTAT is not very effective whereas CTAT should be used.
(see page 488)
10. How are in-phase (I) and quadrature (Q) components
of an RF signal generated?
a) With a 90° (hybrid quadrature) equal amplitude power coupler
hybrid quadrature coupler uses an effective 1/4-wavelength additional length in one signal path (usually 3 dB
down = equal amplitude split) to create I (0°) and Q (90°) output signal ports. (see page 608)