11

I have seen diode clamping/clipping circuits and can see that they can work well with such simple construction. However, what if we want to clamp/clip the current to some value rather than voltage?

quantum231
  • 11,218
  • 24
  • 99
  • 192
  • Do you specifically mean some single-part mechanism like diodes, or would any combination of parts satisfy your query? – Anindo Ghosh Jan 09 '14 at 09:12
  • I just want to see a circuit that can be used to clip/clamp current to a desired value. It can be simple or made up of many parts. I am just curious to know how this is done. – quantum231 Jan 09 '14 at 09:46
  • 1
    http://en.wikipedia.org/wiki/Current_limiting – JimmyB Jan 09 '14 at 09:59
  • 1
    http://320volt.com/en/12v-ve-5v-600ma-irf9530-mosfetli-akim-sinirlama-devresi/ ... and for a 2-terminal device, a [constant-current diode](http://en.wikipedia.org/wiki/Constant-current_diode) – Anindo Ghosh Jan 09 '14 at 10:11
  • See also [The FET Constant-Current Source/Limiter](http://www.vishay.com/docs/70596/70596.pdf), the section on "Standard Two-Leaded Devices". – Tut Jan 09 '14 at 11:55

1 Answers1

8

Here are a bunch of constant current circuits that I found while googling "contant current circuit: -

enter image description here

  1. This is the classic use of a transistor - the load is in the collector and you set the bias on the base so that there is a certain voltage across R1 - if that voltage is 3.3V then, due to R1 being 3k3, no more than 1mA can be passed to the load.
  2. If the LED (or load) tries to take more current than a certain value the lower NPN transistor starts to switch on the reduces the base voltage on the darlington thus current limiting is achieved.
  3. This is the classic use of the LM317 regulator chip
  4. This is a fairly simple and accurate current limit circuit. The voltage across R2 is held at (V+ -Vref) by action of the op-amp and transistor - this means the load (connected to the emitter) cannot draw more current than (V+ -Vref)/R2.
  5. This is the same as (4) (sorry, my mistake)
  6. This is very similar to (2) but works with a +V referenced load.
  7. This is similar to (4) and (5) but uses a MOSFET as the current limiting element.

With voltage limiting the word clamping is often used. With current, the term used is often "limiting".

Andy aka
  • 434,556
  • 28
  • 351
  • 777