TTL-NOT Versus CMOS-NOT

131

02:23:04

The CMOS version has a quicker rise and a fall of the same length, and the TTL has a slower rise but near-instant fall. Also, the CMOS is much more compact and doesn't use any current on idle while the TTL is much bulkier and uses resistors that take up a lot of space in ICs and consumes 7-4mA on idle. Also, I'm wondering what's up with that backwards transistor in the TTL. Maybe it's supposed to be utilized in both directions, the low reverse beta being used in the other direction.

published 8 years ago

BillyT

8 years ago

Where did the TTL circuit come from?

hurz

8 years ago

In the early days of TTL there were no other technologie available. So, it wasn't a question about TTL or CMOS. TTL was the state of the art, and the fastest/efficient logic family available.

hurz

8 years ago

BTW, the resistor values are by far not correct, anyway the correct ones doen't change a lot the speed behaviour.

jason9

8 years ago

@BillyT, google images. @hurz, the image I took the circuit from didn't happen to include the resistor values. Also, I know that TTL was used a long time ago and then CMOS came into existence and seemed better and has been used ever since. I was simply comparing the two, showing their advantages and disadvantages.

BillyT

8 years ago

@hurz the reason I asked Jason9 the origin is that the circuit seams over complicated. Just a bit of my background, when I learned electronics, everything was TTL.

hurz

8 years ago

@BillyT, for me the topology looks ok, this is the way TTL implement an inverter. But as expected the resistor values are wrong. Base resistor at input BJT must be more in 4k collector output resistor is more in the range of 100 Ohm.

jason9

8 years ago

I changed the resistor values as you said. Is that better?

hurz

8 years ago

Its not better, but its closer to a real implementation. 👍

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