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

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Discussion Overview

The discussion centers around the minimum pulse width required for switching a DC voltage/current, specifically in the context of controlling a stable bias current of approximately 40 mA. Participants explore potential switching ICs and methods for achieving this control within a maximum pulse width of 40 microseconds.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • One participant seeks advice on switching ICs that can operate effectively with a maximum control pulse width of 40 microseconds.
  • Another participant suggests using Analog Switch ICs or a controllable current source but asks for clarification on the application.
  • A different participant notes that many ICs are not designed for DC operation and specifically mentions the need to drive a laser with a stable current.
  • One participant provides links to resources from Maxim and Analog Devices, suggesting that building a switched current source might be a cleaner solution.
  • A participant inquires about the minimum pulse width required for the switching operation and raises considerations about sourcing versus sinking current through the load.
  • Links to documents are shared that may help in designing a simple switched current source with adequate speed and accuracy.

Areas of Agreement / Disagreement

Participants express varying opinions on the best approach to switch the DC current, with no consensus on a specific IC or method. There is also uncertainty regarding the minimum pulse width needed for effective switching.

Contextual Notes

Participants have not fully defined the assumptions regarding the application or the specific requirements for the switching mechanism, which may affect the recommendations provided.

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

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