Hello, I'm a University student, and I want to make a Current Source by using Holwland's Pump so no Transistor or Diode will be used. The problem is that I only have 5 V for supply (A cellphone charger) So, I would like to know if you can give me advise of what OpAmp to use. And resistor values.

Also, If you know any other circuit examples for Current Source using one or more OpAmps would be really great.

 

So, a 5 volt supply and you want to get an unknown amount of current from an unknown input. I would say, Use an unknown op-amp with unknown resistor values. As for examples of other op-amp based current sources, I would suggest Google.

 

So, a 5 volt supply and you want to get an unknown amount of current from an unknown input. I would say, Use an unknown op-amp with unknown resistor values. As for examples of other op-amp based current sources, I would suggest Google.

Yeah Sorry, I would like to get at least 20 mA. It wasn't really necessary to be sarcastic.

 

If you can't tell about what input you want to cause 20 ma to flow, I suggest reading this:

 

If you can't tell about what input you want to cause 20 ma to flow, I suggest reading this:

I wonder why they removed Bob Pease's name from the app note: http://forum.allaboutcircuits.com/attachments/howland-current-pump-pdf.42132/

 

There have been several threads about the Howland pump. Here's ond of the most detailed: http://forum.allaboutcircuits.com/threads/ideal-opamp-circuit.20636/

 

I wonder why they removed Bob Pease's name from the app note: http://forum.allaboutcircuits.com/attachments/howland-current-pump-pdf.42132/

Hi,

I think that is a very sad and unprofessional way to handle that kind of Revision. Bob was an iconic figure for years at National and i find it reprehensible to just blandly remove his name from material he took great lengths to get right and informative. That's a big corp for you. More for them, less for everybody else. I guess they figure they own the copyright to all that stuff now so they can do anything they want with it. I also see this as possibly their strive to be the big boss which means they like to try to erase any other informative head so they can appear to have all the knowledge from the stem to the current time. They did this back in ancient Egypt a few times too when the new leader wanted to appear to be the god head, which made them look better and apparently so they could rule more effectively...they would destroy statues of the previous leader or deface them and place their own likeness in it's place.
Bob is probably rolling over in his grave, or at least wondering how they could be such jerks about this.
I have to wonder if we will never see his name again in a newer publication, one that he is mostly responsible for. Very sad.

LATER:
A little analysis of the improved HCP reveals that with an ideal op amp the output current is independent of the value of the load, but after applying some non ideal conditions like finite gain, input impedance, input offset, and output impedance, we see a small dependence start to show up. The following expression for Iout shows this relationship:
Iout=(16666683517*I1-6666666483*I2-1700)/(17*RL+1666683667)

Here we see some offset, some input imbalance, and a small dependence on the load resistor RL. The conditions for the op amp used for this calculation were:
Vinputoffset=1mv
Rin=1Meg
Rout=1 Ohm
A (gain of op amp)=100000