# some questions ????

#### sunil_r_sp

Joined Feb 18, 2007
13
1) We can create an oscillator using an odd no: of nand,not etc.....(since the frequency depends on the propagation delay, definitely we can achieve high clock frequency, so can we replace the crystal oscillator in our computer by this clock ?
2) What is the exact definition of an amplifier ?
3) What is metastability in flip-flopes ?
4) is there something called the 'zero hold time' flip-flop ?

#### beenthere

Joined Apr 20, 2004
15,819
1. The purpose of the crystal in the oscillator circuit is for frequency stability. Substituting 3 - 5 inverter elements will oscillate, but things like temperature, power supply variation, other circuit operation, and just about any other variable will have some effect on the frequency. This is not a way to achieve stability.
3. They can be in one of two states, or in a transition from one to the other.
4. If I understand this as meaning that the set or reset state would not be latched, then what would be the purpose of that logic element?

#### Dave

Joined Nov 17, 2003
6,969
4) is there something called the 'zero hold time' flip-flop ?
Are you confusing this with zero order hold flip-flops?

Zero-order hold and zero hold time are very different concepts.

Dave

#### bloguetronica

Joined Apr 27, 2007
1,541
1) We can create an oscillator using an odd no: of nand,not etc.....(since the frequency depends on the propagation delay, definitely we can achieve high clock frequency, so can we replace the crystal oscillator in our computer by this clock ?
...QUOTE]

You can create a clock generator using three not gates. This is a series resonant clock generator (as oposite to paralel resonant clock oscillator, because the NAND gates, working as 180º out-of-phase amplifiers, are in series).
Also you can create a paralel resonant oscillator, but you will have more problems.