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Tips on choosing components
*Specify supplier: adadruit,,, etc. otherwise, the instructor won’t know where
to purchase the part.
*Check the mounting type and get through-hole. The two most common styles are through hole and
surface mount. Plan on using through hole, on left in picture below (easier to work with but bulkier).
Figure 1. Through hole mounting style on left; surface mount on right
*Use IC sockets. This allows you to instantly replace a bad IC. Otherwise, you are stuck trying to
desolder all N = 8-132) contacts (major pain!). Make sure to get the right footprint. Typically, throughhole chips are 0.3” wide, and have legs spaced at 0.1”: Here are two common styles:
Figure 2. DIP chip “carriers” or IC sockets. Standard style is shown at right; low profile IC socket is shown at right. Doesn’t
really matter which kind unless space is really important, in which case you’d use surface mount devices anyway.
*Remember power connections/battery holders Gotta power the device somehow. If you are
planning on plugging into the wall, make sure get a connector of some sort to bring power to the board.
If you plan to use battery, make sure you get one or more battery holders:
Make sure you get the right IC for the job:
* Comparators: there are op-amps specifically made for this purpose. LP339 is a fine choice:
* Tristate buffers. Make sure there is a one-to-one correspondence between control inputs and number
of switches (some are designed where 1 control enables 4 switches at once). 74HCT125 is a good
*General purpose op-amps will almost surely be run in single supply configuration. This just means you
power the chip with +Vcc and ground (not +Vcc and –Vcc, which is “dual supply”). Rail to rail action is a
bonus (bottoming out at 1.4 V is kinda lame when there’s only 5V dynamic range).
Some good options are: OP2341 and the AD820:
*Rail-splitters Single supply op-amps require a ‘virtual ground’ that sits at a voltage +Vcc/2 (instead of 0
V). The TLE2426 is a good choice:
Note that you can make your own rail-splitter with a voltage divider and op-amp configured as buffer.
Also, see information on course website about Single Supply Op-amp design.