# I to I amplifier .. How to improve it?

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#### taoybb

Hello everyone,

I have question about 'Ground loaded I-I (Current to Current) Amplifier'. My teacher gave me this one. He said try find the way to improve this.

Only Maximum of 2 Op-amp are allowed, It will be great if I use only one of it. And unlimited amount of resistor can be use. Just two on these component. And it's must be 'Ground Loaded'. Here is circuit.

An externally hosted image should be here but it was not working when we last tested it.

#### Mark Johnson

Paid Member

I think your professor wants you to make a plot of input current (from the independent current source on the left) versus output current (flowing in R2 and in the LOAD).

Then I think your professor wants you to design a new circuit whose output current is pi times the input current (pi = 3.14159265...).

Finally I think your professor wants you to install a potentiometer (variable resistor) in your circuit, so the output current is "K" times the input current, where "K" can be adjusted by twirling the shaft of your potentiometer.

#### jan.didden

Paid Member
Or maybe he wants you to convert this to a current-to-current amplifier instead of the current-to-voltage amplifier it is now.
That could be done by interchanging R2 and Rload

Jan

#### DF96

taoybb said:
I have question about 'Ground loaded I-I (Current to Current) Amplifier'. My teacher gave me this one. He said try find the way to improve this.
Did your teacher mean 'ask someone else to find a way to improve this' or did he mean 'you, my student, work out for yourself a way to improve this'. It all hangs on what he meant by "find": 'go and look' or 'go and think'. Is this a course on research methods or circuit design?

#### taoybb

I think your professor wants you to make a plot of input current (from the independent current source on the left) versus output current (flowing in R2 and in the LOAD).

Then I think your professor wants you to design a new circuit whose output current is pi times the input current (pi = 3.14159265...).

Finally I think your professor wants you to install a potentiometer (variable resistor) in your circuit, so the output current is "K" times the input current, where "K" can be adjusted by twirling the shaft of your potentiometer.

Or maybe he wants you to convert this to a current-to-current amplifier instead of the current-to-voltage amplifier it is now.
That could be done by interchanging R2 and Rload

Jan

He want me to find disadvantage of this circuit then fix it or make an improved version by using only Op-amp and resister (Only 2 op-amp are allowed). I only find one, it's gain will be change when load change.

Oh! Another info I forget to tell, Another name of this circuit is 'Howland Current Source'.

Did your teacher mean 'ask someone else to find a way to improve this' or did he mean 'you, my student, work out for yourself a way to improve this'. It all hangs on what he meant by "find": 'go and look' or 'go and think'. Is this a course on research methods or circuit design?
It's not a class just out from class, So it might not that important but I want to try. I got it for few day and still have no idea how to improve it yet. So I came here to ask someone to guide me how should it be and any idea which help me improve it.

#### jan.didden

Paid Member

He want me to find disadvantage of this circuit then fix it or make an improved version by using only Op-amp and resister (Only 2 op-amp are allowed). I only find one, it's gain will be change when load change.

Oh! Another info I forget to tell, Another name of this circuit is 'Howland Current Source'.

It's not a class just out from class, So it might not that important but I want to try. I got it for few day and still have no idea how to improve it yet. So I came here to ask someone to guide me how should it be and any idea which help me improve it.

It's 'Howland Current Pump'. So he wants it to be a current in - current out circuit.
Google Howland Current Pump will help you find an app note by a guy called Bob Pease on the HCP.

Edit: try the attached

Jan

#### Attachments

• howland current pump AN-1515.pdf
227.6 KB · Views: 80
Last edited:

#### taoybb

It's 'Howland Current Pump'. So he wants it to be a current in - current out circuit.
Google Howland Current Pump will help you find an app note by a guy called Bob Pease on the HCP.

Edit: try the attached

Jan

Oh, Thanks you. "Howland Current Pump" , hahaha I just always try search something like 'Current to Current' and other and found nothing help. Thanks you for right keyword and attachment. this look interesting and this might help me a lot.

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