A couple of questions

[Varun]

I've a few questions I am sure that you gurus can answer.

First off, what exactly produces light in an LED? We can all see where the light comes from when looking at a light bulb, but what makes an LED an LED and how is it so efficient?

When talking about CPU's, die size is always talked about. What exactly is the die size representing?

Finnaly, does anyone know a TTL device that allows a divide by anything other than 2^x? I'd like to divide a 4MHz clock signal to 45Hz, but dividing by 2 I can only get 30 or 60Hz.

Thanks!

 

[CTho9305]

Originally posted by: Varun
I've a few questions I am sure that you gurus can answer.

First off, what exactly produces light in an LED? We can all see where the light comes from when looking at a light bulb, but what makes an LED an LED and how is it so efficient?

Google direct gap semiconductors. I don't remember the explanation, but that search should tell you.

When talking about CPU's, die size is always talked about. What exactly is the die size representing?

How much wafer space a single CPU takes up. Smaller die size means you can fit more per wafer, and each one will cost less. You can fit more stuff in more space though, so it's a tradeoff.

 

[Mark R]

Finnaly, does anyone know a TTL device that allows a divide by anything other than 2^x? I'd like to divide a 4MHz clock signal to 45Hz, but dividing by 2 I can only get 30 or 60Hz.

A counter. Use the clock to increment a counter - reset the counter when the appropriate divisor is reached, and use the reset signal for your timebase. Of course, you need an appropriate time source to start with - 4 MHz, won't give you exactly 45 Hz you'll have to settle for 45.00045. You'll have to decide whether that is an acceptable level of accuracy.

 

[Varun]

Originally posted by: Mark R

Finnaly, does anyone know a TTL device that allows a divide by anything other than 2^x? I'd like to divide a 4MHz clock signal to 45Hz, but dividing by 2 I can only get 30 or 60Hz.

A counter. Use the clock to increment a counter - reset the counter when the appropriate divisor is reached, and use the reset signal for your timebase. Of course, you need an appropriate time source to start with - 4 MHz, won't give you exactly 45 Hz you'll have to settle for 45.00045. You'll have to decide whether that is an acceptable level of accuracy.

Brilliant! Thanks I'll set that up today!

Thanks for the LED and die size answers too.

 

[Bleep]

their is another way to get whatever frequency you want and that is by hetrodyning. You mix 2 frequencies together and you get a sum frequency and a difference frequency just trap out the one that you dont want with a little LC circuit.

Bleep

 

[Varun]

Thanks for the advice Bleep, and I should have stated this, but I am hoping to do this in programable logic and not with seperate circuits.

Due to a Blizzard in my area I have not got a chance to try the counter yet.