Author Topic: Voltage Controlled Current Source Question  (Read 3002 times)

0 Members and 1 Guest are viewing this topic.

Offline bobbbyyyTopic starter

  • Newbie
  • Posts: 3
Voltage Controlled Current Source Question
« on: June 09, 2013, 12:03:13 pm »
I'm trying to use one DAC to control multiple N-channel MOSFETs each with identical loads. The objective is for all MOSFETs to output the same amount of current with respect to each other and have a linear relationship to the DAC's output voltage.

I researched voltage controlled current source circuits and simulated the attached circuit I found. It looks like the circuit is doing exactly what's needed but the op amp input voltage is reduced to a range between 0 to 110 mV instead of a wider range (see attachment for op amp input voltage vs MOSFET output current graph).

The sense resistor (R3) is set to 1 Ohm. If it's increased, the input voltage range changes but the maximum current that can be sunk from the MOSFET gets reduced (not wanted).
How can I get a wider input voltage range for such a circuit (0V to 3V for example)?
Is there another circuit that I should look into instead of this one?
« Last Edit: June 09, 2013, 12:05:50 pm by bobbbyyy »
 

Offline David_AVD

  • Super Contributor
  • ***
  • Posts: 2958
  • Country: au
Re: Voltage Controlled Current Source Question
« Reply #1 on: June 09, 2013, 12:14:33 pm »
Simple voltage divider on the input?
 

Offline bobbbyyyTopic starter

  • Newbie
  • Posts: 3
Re: Voltage Controlled Current Source Question
« Reply #2 on: June 10, 2013, 01:37:26 am »
Simple voltage divider on the input?
That works perfectly. Thanks!
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf

 

- - -
-->