Thanks for your fast response Wagner,

At 03:50 PM 3/13/99 -0500, you wrote:
>Sean, cmos circuits, has the nasty habit to oscilate if
>the unused inputs at not referenced to ground or Vcc...

Yes, I understand this,and I have all the other inputs on the IC tied,but
since I want to use this inverter as an amplifier,I can't tie its input to
one of the rails, I have to use it as an input. Are you saying that I must
use a very low impedance to drive it? I tried that,by using an FET as a
buffer,but I still got oscillations,although,the waveform was more complex.

>
>This is a common mistake, from the TTL age, when leaving
>an unused input floating it was considered HIGH level.
>
>In the 74HC or HCT or other families it is a disaster.
>A small oscilation in the air static caused by a butterfly
>flying in China, make that unused output to flip, and it
>will feedback to the input by some internal ways, it turns
>to be a strong oscillator, also killing your batteries...
>be aware.  Just connect unused inputs to Vcc or Ground.
>I choose Ground, since the output goes high (in inverters)
>consuming less power.

Ok,but why would it consume less power in the high state than the low
state? Do NMOS transistors have lower leakage current with their gates tied
to zero?

>
>--------------------------------------------------------
>Wagner Lipnharski - UST Research Inc. - Orlando, Florida
>Forum and microcontroller web site:  http://www.ustr.net
>Microcontrollers Survey:  http://www.ustr.net/tellme.htm
>

Thanks again,

Sean

|
| Sean Breheny
| Amateur Radio Callsign: KA3YXM
| Electrical Engineering Student
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