Mixing 4000 and 7400 Series

M

Michael

Guest
Hi,

I have a circuit that is made up of 4000 series CMOS ICs but it needs a
magnitude comparator to work and I only have the 74LS85. Is there anyway I
can use this so I don't have to order the 4063 CMOS comparator?

Thanks in advance,

Michael
 
On Mar 16, 4:47 am, "Michael" <mQiQcQhQaQe...@QmQhQiQmQsQ.QcQoQ.QuQkQ>
wrote:
Hi,

I have a circuit that is made up of 4000 series CMOS ICs but it needs a
magnitude comparator to work and I only have the 74LS85. Is there anyway I
can use this so I don't have to order the 4063 CMOS comparator?

Thanks in advance,

Michael
Click to expand...
Your 4000 series slows down at 5V and your LS blows up over 5V. Is
that acceptable?

Mixing logic families is mostly OK but things like reset/preset are
often logic low for TTL and high for CMOS along with limited drive
from CMOS. I'm sure most everyone has done it at some time. I know I
have.

GG
 
<stratus46@yahoo.com> wrote in message
news:dca188eb-4e85-40f6-9060-565154e9f956@i29g2000prf.googlegroups.com...
On Mar 16, 4:47 am, "Michael" <mQiQcQhQaQe...@QmQhQiQmQsQ.QcQoQ.QuQkQ>
wrote:
Hi,

I have a circuit that is made up of 4000 series CMOS ICs but it needs a
magnitude comparator to work and I only have the 74LS85. Is there anyway I
can use this so I don't have to order the 4063 CMOS comparator?

Thanks in advance,

Michael
Click to expand...
Your 4000 series slows down at 5V and your LS blows up over 5V. Is
that acceptable?

Mixing logic families is mostly OK but things like reset/preset are
often logic low for TTL and high for CMOS along with limited drive
from CMOS. I'm sure most everyone has done it at some time. I know I
have.

GG

Thanks,

The circuit is spread across multiple PCBs with this CMOS/TTL problem on
it's own board. So in theory I should (and can) increase the supply voltage
on the CMOS bits of the circuit and keep the TTL parts still at 5V? That
should reduce the operating speed difference somewhat correct?

There's no reset type pins it's just purely data that will be sent between
the two that makes thing's slightly simpler.

Cheers,

Michael
 
On Mar 16, 5:47 am, "Michael" <mQiQcQhQaQe...@QmQhQiQmQsQ.QcQoQ.QuQkQ>
wrote:

I have a circuit that is made up of 4000 series CMOS ICs but it needs a
magnitude comparator to work and I only have the 74LS85. Is there anyway I
can use this so I don't have to order the 4063 CMOS comparator?
Click to expand...
A 4000 series CMOS gate will drive ONE 74LS series standard
input adequately, provided (1) the CMOS has 5V power supply
and (2) the two chips are at the same temperature.
CMOS sinks inadequate current when it's hot for a 74LS
input when that LSTTL chip is cold.

And, an output from a 74LS gate will drive a CMOS gate adequately
if you add a pullup resistor (for highest performance, 4k ohms to +5V).
 
On 3ÔÂ16ČŐ, ĎÂÎç8Ęą47ˇÖ, "Michael" <mQiQcQhQaQe...@QmQhQiQmQsQ.QcQoQ.QuQkQ>
wrote:
Hi,

I have a circuit that is made up of 4000 series CMOS ICs but it needs a
magnitude comparator to work and I only have the 74LS85. Is there anyway I
can use this so I don't have to order the 4063 CMOS comparator?

Thanks in advance,

Michael
Click to expand...


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On 3ÔÂ16ČŐ, ĎÂÎç8Ęą47ˇÖ, "Michael" <mQiQcQhQaQe...@QmQhQiQmQsQ.QcQoQ.QuQkQ>
wrote:
Hi,

I have a circuit that is made up of 4000 series CMOS ICs but it needs a
magnitude comparator to work and I only have the 74LS85. Is there anyway I
can use this so I don't have to order the 4063 CMOS comparator?

Thanks in advance,

Michael
Click to expand...


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contracts, arrange shipping or monitor product quality? Don't worry -
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Audio, and Computer Accessories now by visiting the online wholesale
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products, and easy secure payment by credit card through Paypal.

Selling on eBay or your own online store? Send products direct from
our warehouse to your customers using our unique drop-shipping
service. You can profit by selling hundreds of different products,
without holding any of your own inventory! Any questions you have will
be answered by the seriouswholesale English-speaking customer support
team... Their aim is to make your China electronics importing business
easier to run than ever before.

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