# Circuit problem

Need help with circuit problem---I need to convert a simple dc circuit---approx 3 v---into pulses---perhaps as rapid as nanoseconds in betw pulses---however not yet sure of freq----also dc polarity would remain the same. Is there any component or device that could act as an ultra rapid on off switch--??-----

Randy Rosenthal

berkeman
Mentor
Need help with circuit problem---I need to convert a simple dc circuit---approx 3 v---into pulses---perhaps as rapid as nanoseconds in betw pulses---however not yet sure of freq----also dc polarity would remain the same. Is there any component or device that could act as an ultra rapid on off switch--??-----

Randy Rosenthal

Welcome to the PF.

Do you mean just a canned oscillator?

You can get them in many different frequencies, and they are available with power supply inputs of 3.3V (and maybe there are some 3.0V ones too). They will generally be 50% duty cycle, though. Is that what you want?

One of the first requirements in designing a circuit is defining exactly what the circuit should do and determining as many of the parameters of the circuit as you can. Without knowing these things you really have no where to start. You can't even determine if you want to use transistors or an integrated circuit.

As a minimum you should know maximum allowable rise time and fall time, minimum pulse width and minimum time between pulses. Will the pulse widths and time between pulses always be the same or variable? What is the minimum acceptable voltage of your pulses and the maximum low voltage between pulses? What will be your load - resistive, capacitive or inductive and what will be its impedance. How will you verify your circuit is working?

There used to be a saying for computer programming that the sooner you start, the longer it will take. The idea was that you need to think very carefully about what you want to do and how to do it before you ever start designing.

vk6kro
You can get 100 MHz oscillator modules like this:

http://cgi.ebay.com.au/RALTRON-CRYS...lectrical_Equipment_Tools&hash=item4a9fc37064

You can click on that link or look up the following Ebay number:

320507965540

These oscillators have an output that is near +3 volts for 5 nS, and near zero volts for 5 nS giving a period of 10 nS or a frequency of 100 MHz.

This is a price for 10 of these, but as you can see, they are not expensive. They are usually not very accurate either and could be 1000 Hz off frequency at 100 MHz. Better accuracy is available at extra cost.

Tnx for the info----merry xmas----RR