8 input NAND gates

Thread Starter

Dominick

Joined Dec 6, 2008
28
Hello everyone,
first time to this site and forums and was hoping you could help my with something.
I have been looking for an 8input NAND gate, looks like mouser sold them
but have discontinued them any other places?

If this is any help I technically need a 7 input but an 8 was close enough
so I coupled one input to + to get my 7.
 

mik3

Joined Feb 4, 2008
4,843
If you can't find a 8 input NAND gate you can take two 4 input NAND gates and wire their outputs into the inputs of a 2 inputs NAND gate to make a 8 input NAND gate.
 

beenthere

Joined Apr 20, 2004
15,819
You need to specify a logic family before we can make good suggestions. Old 74xx TTL isn't compatible with anything but 74LSxx. 4000 CMOS and 74HCTxx are lots more available.
 

Ron H

Joined Apr 14, 2005
7,063
If you can't find a 8 input NAND gate you can take two 4 input NAND gates and wire their outputs into the inputs of a 2 inputs NAND gate to make a 8 input NAND gate.
That doesn't make an 8 input NAND. If you take two 4 input NAND gates and wire their outputs into the inputs of a 2 input NOR gate, and follow that with an inverter, which can be made from another NOR gate, you will have an 8-input NAND.
 

Thread Starter

Dominick

Joined Dec 6, 2008
28
You need to specify a logic family before we can make good suggestions. Old 74xx TTL isn't compatible with anything but 74LSxx. 4000 CMOS and 74HCTxx are lots more available.
WoW apparently I am out of touch with electronics these days. :(
Are there any cross reference books out there?
Worst thing about it is im using an old version of electronics workbench
because I can afford anything else lol.
 

SgtWookie

Joined Jul 17, 2007
22,230
You could use a CMOS 4073 or a TTL 74x11, which are both triple 3-input AND gates.

Run the outputs of two of the gates to two of the inputs of the 3rd gate.

This leaves you with a 7-input AND gate. Then run the output through an inverter.
 
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bertus

Joined Apr 5, 2008
22,270
Hello,

Here are two pages of the wikipedia that will give an overview:
1) the old 74XXX TTL serie
http://en.wikipedia.org/wiki/List_of_7400_series_integrated_circuits
2) the newer 4XXX cmos serie
http://en.wikipedia.org/wiki/List_of_4000_series_integrated_circuits

Here are also some links on digital electronics of the EDUCYPEDIA:
http://www.educypedia.be/electronics/digital.htm

There are more pages like that over there:
Digital electronics:
Arithmetic circuits D/A-A/D converters Number systems Codes and decoders Flip flops Technology Counters and registers General overview Technology-CMOS Digital logic Memories Technology-TTL Timers and oscillators


Greetings,
Bertus
 

Thread Starter

Dominick

Joined Dec 6, 2008
28
Thanks bertus most appreciated, I have not built any projects since I got out of school back in 1999.
Now that I want to start my HO scale model railroad back up I will be getting back into building all my own electronics for it.
 

bertus

Joined Apr 5, 2008
22,270
Hello,

The drawing with the 74145's is correct.
The outputs are open collector outputs.
The outputs may be connected.
See the picture on the site :



Greetings,
Bertus
 

SgtWookie

Joined Jul 17, 2007
22,230
The 4017 would only work if you had open-collector transistors (or open-drain MOSFETs) on each output. You can't simply wire the outputs together as you can with the 74x145; as the latter DOES have open-collector outputs.

You could use a ULN2803 or ULN2804 (depending upon your logic voltage) as a driver IC; both contain eight Darlington pairs; the main difference between them is the input base resistance. The 2804 is for 6-15v CMOS logic.

You might be interested in a slightly different approach; a 4017 timer where the duration of each output (0-9) can be set separately. See the attached for the basic idea.

In your case, you'd use Q0 as a normal timer (like the others). This circuit originally came about due to someone wanting a timer that had variable times between output pulses. It would be very easy to adapt this to traffic light controls.

4093 quad NAND gates (with the inputs for each gate tied together) could be used instead of the 40106 inverters, but you would only get 4 gates per IC instead of six inverters.
 

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Thread Starter

Dominick

Joined Dec 6, 2008
28
bertus I knew you can connect them together but electronics workbench did not like that would not do a simulation right.
and as of right now I can't seem to get circuit maker 2000 to do a simple
sim. keeps giving me an error even on a simple 555 timer.
 

Thread Starter

Dominick

Joined Dec 6, 2008
28
Thanks I was just trying to get some thing running before I bought
any components because the circuit I'm making is alot larger than just the traffic lights.
 

Wendy

Joined Mar 24, 2008
23,415
For large input circuits I tend to use diode gates. Diodes can actually take less board space than chips, and bridge gaps better.
 

mik3

Joined Feb 4, 2008
4,843
That doesn't make an 8 input NAND. If you take two 4 input NAND gates and wire their outputs into the inputs of a 2 input NOR gate, and follow that with an inverter, which can be made from another NOR gate, you will have an 8-input NAND.
Ohhhh yes. Thanks for the correction, I got confused with AND gates.
 
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