>> The 7400 is a quad 2-input NAND gate. In other words, it's a box with 
>> four NAND gates in it.
>>
>> What's supposed to happen is that you connect pins 1 and 14 to a power 
>> source, and the remaining pins are grouped into 3s. Each group is the 
>> connections for a single NAND gate. When the inputs aren't connected, 
>> the output pin is at logic high. When you connect both of the input pins 
>> to the (+) rail, the output should go low.
>>
>> ...except this doesn't seem to happen. I swear to God I built circuits 
>> like this when I was a kid, and it worked. But when I tried it as a 
>> teenager, it wouldn't work for toffee. No idea why.
> 
> 
> Good grief Andrew, 7400s, did you rob a museum?

Maplin.

IIRC, they charge 21.22p per chip. (Presumably the 0.22p only makes a 
difference if you buy hundreds of them...)

> Do you know the power consumption of TTL compared to CMOS?

TTL has the advantage that it doesn't break if you touch it. ;-)

> Besides pin 14 being Vcc and pin 7 ground.

OK. I was going from memory there.

> You cannot assume that inputs will
> float high you really should drive them high or low.

...?

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

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