What is the minimum pulse width for switching a DC voltage/current?

[thavamaran]

Hi guys. I recently posted to discuss on switching signals. I have resolved that.

Now, I am trying to switch a DC voltage/current.

Say I am supply a DC stable bias current of about 40 mA. If I want to switch it off at certain time interval, maximum of 40 us. Which means, the maximum pulsewidth of the control pulse will be 40 us.

After 40 us, I don't want any direct current to go through the switch.

Can anyone suggest a switching IC operates at this region? I googled it, and I don't seem to get a right answer.

Any advice please?

 

[berkeman]

Hi guys. I recently posted to discuss on switching signals. I have resolved that.

Now, I am trying to switch a DC voltage/current.

Say I am supply a DC stable bias current of about 40 mA. If I want to switch it off at certain time interval, maximum of 40 us. Which means, the maximum pulsewidth of the control pulse will be 40 us.

After 40 us, I don't want any direct current to go through the switch.

Can anyone suggest a switching IC operates at this region? I googled it, and I don't seem to get a right answer.

Any advice please?

You can use Analog Switch ICs, or you can make a controllable current source. What is the application?

 

[thavamaran]

Most IC's that I have seen doesn't operate in DC. Its for biasing a laser. We have to supply a certain amount of current, say 40 mA to drive it.

I just want to switch it off at some time interval. Do you have suggestion. Thanks for your reply.

 

[berkeman]

Maxim and Analog Devices make lots of analog switch ICs:

http://www.google.com/search?tbm=is...18&q=analog+switch&gbv=2&aq=f&aqi=g5&aql=&oq=

It would be cleaner to just build up a switched current source. Do you have an EEs working on this project?

 

[thavamaran]

Hi Berkeman. Do you have any example of a switched current source. Its just me working in this project. Cheers.

 

[es1]

You mention the maximum pulse with is 40uS.
What is the minimum?

Also, you'll want to decide if you want to pull current though the load or source current into the load.
http://www.automationdirect.com/static/specs/sinksource.pdf

Anyway, if you want to source current from the supply section 4 and 5 in this document show how to make a simple one that will be fast enough to settle in a few uS and have ok accuracy.
http://www.tedpavlic.com/teaching/osu/ece327/lab1_bjt/lab1_bjt_transistor_basics.pdf