Folding/Folded Amplifier -> Current Source Design

Thread Starter

connor maynes

Joined Apr 26, 2018
3
I am designing a folding amplifier. Currently, the design works with an ideal current source; however, my end goal is to implement the circuit on a breadboard and then a PCB. I have already attempted to use a current mirror, but this does not work as the current fluctuates.

Could someone please give me some suggestions, keeping in mind I am a novice?

Here are the files thus far:
https://drive.google.com/drive/folders/1w6JczNHLYZ1Xf-7aiAARTZIr-SF3H00S?usp=sharing
 

crutschow

Joined Mar 14, 2008
26,440
The "current fluctuates" tells us little.
How much does it fluctuate, over what conditions, and what is the maximum fluctuation you can tolerate?
 

Thread Starter

connor maynes

Joined Apr 26, 2018
3
I will try to be clearer. I expected nearly perfectly constant current from the current mirror, but instead I get the following when I run a DC sweep on the input voltage Vin from 0 to 1 V in steps of 0.001.

 

Thread Starter

connor maynes

Joined Apr 26, 2018
3
I am designing a folding amplifier. Currently, the design works with an ideal current source; however, my end goal is to implement the circuit on a breadboard and then a PCB. I have already attempted to use a current mirror, but this does not work as the current fluctuates.

Could someone please give me some suggestions, keeping in mind I am a novice?

Here are the files thus far:
https://drive.google.com/drive/folders/1w6JczNHLYZ1Xf-7aiAARTZIr-SF3H00S?usp=sharing
Uploaded files to this forum...
 

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crutschow

Joined Mar 14, 2008
26,440
With a transistor Vgs threshold of about 0.68V you don't have a lot of dynamic range to play with.
Using only a 1V supply it's only about 0.3V and it's likely that the transistors are simply cutting off.
Try using higher bias voltages.
 
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