This thread was separated from TTL circuits Help. (NOT, AND, OR, ETC.)
i have read through the e book on the ttl chapter. it a good explaination there.
specifically on nand gate or inverter, I would like to know more detail on how all the transistors in the ttl turned on.
Is it caused by the Base Voltage or the Base Current?
It would be very helpful if someone can explain how the transistors in the TTL turn ON technically. The explaination using the diode does help but doesnt give a clear picture (technically) how Q1 that is OFF state can turn on the next transistor.
Really need help on this. and i thanks u all in advance!
Mod edit: please don't hijack, now you have your own thread.
Scott Wang.
Hi Wendy and all.The thing you have to understand is TTL is not really complex, but the reason it is so popular is in either state it draws about the same current. Other logic families, such as RTL, is much simpler, but when they are in one state the current draw is much different then if they are in the other. The result of this was massive current surges in large circuits, such as early computers. The power supplies had trouble keeping up. With TTL the current was relatively constant.
Our local ebook has a section on TTL...
http://www.allaboutcircuits.com/vol_4/chpt_3/5.html
As a logic family, I much prefer CMOS. It barely sucks current, works over a large range of voltages, has extremely high input impedance (which allows for large fan-outs), and low output impedance (which allows it to go rail to rail to the power supply on the output voltages). The downside is it can barely drive a LED, and sometimes not then.
Understanding all the logic families is important though. I frequently use Diode logic on the fly with other logic types, but you have to understand the requirement of each family to successfully do something like this.
i have read through the e book on the ttl chapter. it a good explaination there.
specifically on nand gate or inverter, I would like to know more detail on how all the transistors in the ttl turned on.
Is it caused by the Base Voltage or the Base Current?
It would be very helpful if someone can explain how the transistors in the TTL turn ON technically. The explaination using the diode does help but doesnt give a clear picture (technically) how Q1 that is OFF state can turn on the next transistor.
Really need help on this. and i thanks u all in advance!
Mod edit: please don't hijack, now you have your own thread.
Scott Wang.