65,536), you will need a THD of
0.001% or better.
tant to know if the input bias current
increases or decreases with temperature and roughly by how much.
Cost versus Performance
Lastly, there are many graphs
displayed in the datasheet. This is
because many of the parameters vary
according to frequency, voltage,
temperature, etc. These graphs indicate how the op-amp performance is
expected to change. Note that these
are usually typical values, so don’t
expect your particular unit to exactly
match these measurements. The
graphs are presented to indicate
response trends, not response specifications. For example, it may be impor-
What’s the difference?
You’re correct, the one on the right costs
less because it’s from Jameco! When
you’re looking to purchase major name
brand passives or semiconductors, be
sure to check out Jameco first. They also
offer money-saving generic equivalents
at about 20% less, so you’ll save even
more! And if you should find a lower
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print-advertised price for a product
Jameco offers, just let them know and
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You can buy the LM741 op-amp
for about a quarter. And quite
honestly, it may be adequate for the
task. But it has an input resistance of
only 300,000 ohms, requires two
power supplies, drifts badly with
temperature, and the noise is not even
specified. You get what you pay for.
I opened my National
Semiconductor Data Book more or
less randomly and found the LPC660.
It has about the same speed as the
LM741 and costs about $3. But for
this price, you get four amplifiers in
one package, so the cost per amplifier
is only about $0.75. It is a single
supply amplifier (from 5V to 15V) with
rail-to-rail outputs, >1 teraohm input
resistance, drifts 1/10 of the LM741,
and uses about 1 mW of current per
amplifier (about 1/100 of the LM741).
(The savings in battery cost far
outweigh the increase in the
The point of this brief comparison
is to show that analog electronics
have evolved substantially. It is truly
amazing what a dollar or two can buy.
But if you don’t know what to look for,
you can’t find the best part for your
money. If you want your project or
product to provide peak performance
and in the most cost-effective manner,
take the time to see what’s available.
Spending a little effort at the start can
provide you with incredible analog
Click or call today for a FREE Jameco Catalog
& start benefiting from Jameco’s Awesome Prices!
Choosing an op-amp requires
matching your needs to the op-amp
datasheet. Blindly assuming that any
op-amp will work in any circuit is
only going to result in frustration and
disappointment. Conversely, using
the proper op-amp can allow you
to do things you never thought were