KB6NU's Ham Radio Blog

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From the trade magazines: Monthly projects, USB power

Posted: 22 Jan 2016 05:54 PM PST
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Interesting Kickstarter: Electronic hobby projects delivered to your
door.Â*As Ive mentioned on many an occasion, Im very much enthused by the
Maker movement in general, and by bringing younger folks like high school
kids into the Maker community in particular.Â*Thus, I was jolly excited to
hear about This Kickstarter Project, which was launched by the folks at
Thimble Electronics.Â*Each month, an orange box will arriveÂ*at your door
containing the components and instructions to build that months electronic
hobby project.
Introduction to USB power delivery. The Universal Serial Bus (USB) has
become very important to ham radio, and one of its most useful features is
its ability to deliver power to connected devices. This introduction not
only gives technical details, but also talks about the history of this
feature.




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2016 Extra Class study guide: E6C - Digital ICs

Posted: 22 Jan 2016 11:46 AM PST
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Interestingly, questions on TTL and a couple of questions on logic symbols
were removed from this section to make way for questions on digital
comparators and programmable logic devices.Dan
E6C Digital ICs: Families of digital ICs; gates; Programmable Logic
Devices (PLDs)

Integrated circuits (ICs) are now an integral part (pun intended) of
amateur radio electronics. There are several different technologies used to
manufacture IC including transistor-transistor logic, or TTL; complementary
metal-oxide semiconductor, or CMOS; and BiCMOS, which uses a combination of
bipolar and CMOS transistors.

CMOS is arguably the most common type of digital IC. An advantage of CMOS
logic devices over TTL devices is that the have lower power consumption.
(E6C05) CMOS digital integrated circuits also have high immunity to noise
on the input signal or power supply because the input switching threshold
is about one-half the power supply voltage. (E6C06)

BiCMOS logic is an integrated circuit logic family using both bipolar and
CMOS transistors. (E6C12) An advantage of BiCMOS logic is that it has the
high input impedance of CMOS and the low output impedance of bipolar
transistors. (E6C13)

Tri-state logic devices are logic devices with 0, 1, and high impedance
output states. (E6C03) These devices can be made with either TTL or CMOS
technology. The primary advantage of tri-state logic is the ability to
connect many device outputs to a common bus. (EC604) When a device’s
outputs are in the high-impedance state, they act as if they are
disconnected.


When working with digital ICs, it is important to recognize the various
symbols for the different types of logic gates. In Figure E6-5, 2 is the
schematic symbol for a NAND gate. (E6C08) In Figure E6-5, 4 is the
schematic symbol for a NOR gate. (E6C10) In Figure E6-5, 5 is the schematic
symbol for the NOT operation (inverter). (E6C11)

When designing circuits with digital ICs, you may not use all of the inputs
of the gates in that IC. To set that input to a digital 1 or 0, you might
use a pull-up resistor or a pull-down resistor. A pull-up or pull-down
resistor is best described as a resistor connected to the positive or
negative supply line used to establish a voltage when an input or output is
an open circuit. (E6C07) Pull-up resistors are also often used on the
output of a digital circuit to prevent that output from floating.

A particular type of IC is called a comparator. Comparators compare an
input voltage to a threshold voltage, and when the level of a comparator’s
input signal crosses the threshold is the comparator changes its output
state. (E6C02)

Comparators have a property called hysteresis. Basically, what this amounts
to is that the threshold voltage at which the comparator switches is lower
when the input voltage is decreasing than the threshold voltage at which
the comparator switches when the input voltage is increasing. The function
of hysteresis in a comparator is to prevent input noise from causing
unstable output signals. (E6C01) If the threshold voltage was the same for
both increasing and decreasing input voltages, and the input voltage was
right at the threshold voltage, then noise could cause that input voltage
to go above and below the threshold randomly. If the comparator input did
not have hysteresis, then its output would switch randomly.

Many modern electronic devices now use programmable logic devices instead
of cobbling together a digital circuit with a collection of ICs with simple
gates. A Programmable Logic Device (PLD) is a programmable collection of
logic gates and circuits in a single integrated circuit. (E6C09).
Programmable logic devices can have thousands or even millions of gates in
a single IC. To design digital circuits with PLDs, designers use
computer-aided design software to connect and configure the logic gates.

A programmable gate array is a particular type of programmable logic
device. The primary advantage of using a Programmable Gate Array (PGA) in a
logic circuit is that complex logic functions can be created in a single
integrated circuit. (E6C14)

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KB6NUs Ham Radio Blog.