Help with obtaining a specific pulse

[malsch]

Homework Statement

Hi, I have a 1Hz pulse and wish to obtain a very short pulse at the low edge of the 1Hz pulse. The following is what I'm referring to:

The Attempt at a Solution

Since I cannot use a capacitor, I was thinking maybe something with flip flops but I'm still a bit stuck.

Thank you

 

[jambaugh]

Do you have more information on the available circuit elements you do have?

My first thought is a transformer (converting rate of change of current to a voltage) and a good stiff diode to filter out the pulse from the descending edge.

 

[vk6kro]

There a lot of these edge detector circuits.

I had to invent one years ago and I tend to use that one all the time.

It works on a rising edge (so you have to invert the input first if you want a falling edge) and it gives a falling pulse (ie 5V then 0V then 5V) so you have to invert that if you want a rising pulse.
In this case, you need both inverters.

In the following circuit, the two NAND gates in the middle form the actual edge detector while 3 of the 4 gates are used as inverters. This is convenient because NAND gates come in ICs with 4 gates in them, like the 74C00.

[PLAIN]http://dl.dropbox.com/u/4222062/edge%20pulse.PNG

 

[Quinzio]

How short do you need the pulse ?
1 millisec, 1 microsec, 1 nanosec ?

Why can't you use a capacitor ?

 

[jambaugh]

Hello, I am new here and though I would just ask this here in this thread since it seems relavent.

I need a 3 volt DC power supply that is pulsed (any kind of pulse shape) at a nanosecond rate.

I am 63 years old and not to savey about present day electronic. I started with a 1B3 rectifr tube.

If a picosecond rate could be acheived it would be great. I just ordered one of those ultra fast step recovery diodes...could that be used to make this PULSE power supply?

Thanks,

David

Hmmm... one nanosecond period corresponds to (hmmm...milli micro nano pico ~ kilo mega, giga tera) a one gigahertz frequency. That's pushing microwave frequencies so you're going to probably need a germanium circuit. You can make a germanium bridge rectifier and a 500MHz oscillator from textbook UHF Ham radio circuits. That will give you a roughly absolute value of a sine wave with peaks spaced 1 nanosecond apart. I'd suggest you check out clock circuits for the newer microprocessor chips as they run in the 1-3 gigahertz range now.

Picosecond rates are getting into low infrared frequencies. One is reaching wavelengths (sub-millimeter) more appropriately considered "optics" rather than "electronics". A one picosecond period equals 1 Tera Hertz frequency. You're not going to find cheap off the shelf parts to put that together. A typical source for such high frequencies is an optically pumped terahertz laser.

 

[lewando]

@zetrone: you should probably start a new thread in case this one gets more involved. Just curious, but how much power are you talking about--what is your "load". Does "pulsed at a nanosecond rate" imply continuous 500MHz operation or do you just want a single fast pulse on demand?