Author Topic: Howland Current Source Circuit  (Read 2271 times)

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Offline wanxingTopic starter

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Howland Current Source Circuit
« on: November 06, 2018, 02:22:01 pm »
Hi, I am trying to design a precision current source circuit of 1A for my project. I found the Howland Current Source circuit when doing some researches, but I am not understand about the working principle or operation of it. Can anyone explain it ? The circuit I found is shown in attachment. Thanks in advance.  ;D
 

 

Offline t1d

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Re: Howland Current Source Circuit
« Reply #1 on: November 06, 2018, 03:52:15 pm »
Well, your question will require a lot of information that is already out there. So, I suggest you do some study and come back, if you have specific questions about certain operations. I often post broad questions, because I do not know where to begin, nor what terms to search. Here is what I think will help you...
1) This is a rather typical constant current source circuit.
2) The heart of the circuit is the operational amplifier.
3) The op amp is fitted with a feedback loop circuit
4) The feedback circuit gives the op amp the "information" needed to adjust the current, to keep it at a consistent level.

I suggest that you look on YouTube, for these tutorials
1) Op Amp operations.
2) Feedback loop circuit operations - both current and voltage.
3) Precision current source circuit.
You probably won't have to spend more than 15 minutes, per subject.

There are special all-in-one ICs, just for this purpose. Check into those, at your favorite supplier. I like Mouser.com.

Do well and we look forward to your future questions.
« Last Edit: November 06, 2018, 04:03:24 pm by t1d »
 
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Offline Zero999

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Re: Howland Current Source Circuit
« Reply #2 on: November 06, 2018, 04:47:17 pm »
The key to understanding it, as with any op-amp circuit, is that the op-amp adjusts its output to make both of its input voltages equal. Here are some links which describe the Howland current pump circuit in more detail. The last one is to a simulator, which can be useful when studying any circuit.
http://www.ti.com/lit/an/snoa474a/snoa474a.pdf
https://www.edn.com/design/analog/4430167/Op-Amp-Current-Sources--The-Howland-Current-Pump
http://www.falstad.com/circuit/e-howland.html
 
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