Test Your EQ
— Issue #156
Each month, Test Your EQ presents
some basic engineering problems for you to test
your Engineering Quotient. What's your EQ?
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Problem
1—Many
RS-232 interface chips, such include a pair of charge-pump
voltage converters to generate ±10-V interface supplies
from a 5-V input. The recommended configuration of external
capacitors is shown below.
Why is the negative end
of C3 connected to the 5-V supply? Would it make any difference
if it were connected to ground?
Answer
Problem
2— Does
the same argument apply to the 10 to -10-V inverter?
Answer
Problem 3—Assuming
the switching occurs at around 100 kHz, how do you select
the size of the capacitors?
Answer
Problem
4—When you know that a number has a single bit
set, you often want to know which bit it is. In other
words, you want to compute the base-2 logarithm of the
number. One way to do this is to write a loop. But, in
this case, that would be O(n), where n is the number
of bits in the word. Can you think of an approach that
would be O(log n)?
Answer
Problem
5— Can
you write a simple test to determine whether or not a
binary number has a single bit set?
Answer
Problem
6—What is the "old" definition of power
factor?
Answer
Problem
7— What is the "new" definition of
power factor?
