74F14 inverter

labview1958 · Post by **labview1958** » Thu Apr 27, 2006 11:03 am

Does anyone know what is the rise time for 74F14 inverter? The rise time for LM319 is 80 ns. How can I imprve the rise time for LM319?

JPKNHTP · Post by **JPKNHTP** » Thu Apr 27, 2006 11:09 am

-JPKNHTP

MrAl · Post by **MrAl** » Thu Apr 27, 2006 12:02 pm

Hi there,

You can pump the output of the LM319 through your 74F14, as
that will have a MUCH faster rise time.

What are you using it for?

Robert Reed · Post by **Robert Reed** » Thu Apr 27, 2006 12:18 pm

Keep your load capacitance to a minimum. This will get you closer to best case rise times.

MrAl · Post by **MrAl** » Thu Apr 27, 2006 1:49 pm

Oh yeah, the rise time of the 74F14 is something like 2.5ns, and
so is the rise time (F family TTL).

labview1958 · Post by **labview1958** » Thu Apr 27, 2006 5:21 pm

How to connect the output of LM319(high speed dual comparator) to the input of 74F14 (Hex inverter schmitt trigger)? It looks to me 74F14 has six inputs and six outputs while I am using only one output from my LM319. Can I choose any one of the six? I am feeding the output from a LM319 to NI 6025E Daq counter. I found out that the counter can only detect TTL signals of rise time less then 50ns. I believe I should connect 74F14 between LM319 and the DAQ board. Help would be greatly apperciated.

dyarker · Post by **dyarker** » Thu Apr 27, 2006 9:50 pm

The LM319 is open collector output. Did you have a pull-up resistor on the connection to the DAQ board? If no, the DAQ was seeing nothing, regardless of switching speed.

Connect LM319 output, with pull-up resistor, to an input on 74F14. One other pull-up resistor to all unused inputs of 74F14. 1KOhm to 3.3KOhm should do.

MrAl · Post by **MrAl** » Fri Apr 28, 2006 5:02 am

Hi again,

I agree with dyarker in that you need a pullup resistor on the
collector of the LM319 output transistor. You also need to ground the
emitter of the output transistor (LM319).

I believe you do well to connect a 74F14 to the output of
the LM319 but you may even get by with a 74LS14 chip.
Yes, the collector of LM319 goes to one of the six inputs
of the 74F14, and if you want you can ground the other
five inputs and leave the five outputs unconnected.

dyarker · Post by **dyarker** » Fri Apr 28, 2006 5:32 am

Grounding unused inputs will work, but I prefer pull-up.

Compare TTL input high current to TTL input low current.

Main thing for any logic family is do not leave any floating inputs!

labview1958 · Post by **labview1958** » Fri Apr 28, 2006 5:41 am

I am looking for an application diagram for 74F14. I have looked at Fairchild and national semiconductor but no luck. Anyone knows where to get one? Basically I want to connect LM to the 74F14 and then to the NI 6025E daq board correctly.

dyarker · Post by **dyarker** » Fri Apr 28, 2006 5:50 am

http://www.fairchildsemi.com/ds/74/74F14.pdf

labview1958 · Post by **labview1958** » Wed May 10, 2006 2:38 am

The link is to a description to the 74F14 and not it's application diagram

I am looking for an application diagram for 74F14. I have looked at Fairchild and national semiconductor but no luck. Anyone knows where to get one? Basically I want to connect LM to the 74F14 and then to the NI 6025E daq board correctly.

JPKNHTP · Post by **JPKNHTP** » Wed May 10, 2006 3:06 am

-JPKNHTP

dyarker · Post by **dyarker** » Wed May 10, 2006 9:00 am

??????? more than a spec sheet for a TTL inverter ??????????????????

Gorgon · Post by **Gorgon** » Wed May 10, 2006 10:42 am

To save power you should pullup all unused inputs via a 2k2-4k7 resistor.
Use the same value for the pullup rsistor on the output from the LM319.

The main problem now is to select the inverter to use.

TOK

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