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Need help with bi directional constant current source (±100mA)
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iMo:

--- Quote from: Hero999 on November 17, 2018, 10:06:34 pm ---
--- Quote from: imo on November 17, 2018, 10:30:37 am ---This gives you nice swing (here aprox 45Vpp) on the output.
The Load is L1=3.5H with R6=5ohm in series (no idea what is the Resistance of your actuator).
Current +/-102.4mA into the Load based on input (here 2.048Vpp sine w/ DC offset +1.024V).
Not easy to simulate, however..
Mind it is a simulation only..
Needs some elaboration with R values and final components of choice..
You may add decoupling, output protection diodes, snubbers, etc. (you mess with inductive load)  :)

--- End quote ---
That circuit doesn't give a voltage offset of 1.024V, but a current offset of 102.4mA.

--- End quote ---
Nope, it is not about an output offset, but DC offset of the input signal generator used in my simulation:

--- Quote ---Current +/-102.4mA into the Load based on input (here 2.048Vpp sine w/ DC offset +1.024V).
--- End quote ---
The OP has got 2 sources at two inputs:
1. a constant +1.024V DC, and
2. the input from a DAC -> 0..+2.048V (=1.024 + 1.024*sin(x), in my simulation).
Therefore my simulation follows his setup..

Of course, the simulation/implementation needs some tweaking, as I wrote above. The important point there is the working principle - the transfer function would be (based on my schematics):

--- Quote ---R1/R3 = R5/R4
Iout = (Vs1-V1)/R8 * R5/R4
--- End quote ---
or something like that :)

Zero999:

--- Quote from: duak on November 18, 2018, 03:24:28 am ---Hero,

I'm not able to simulate yours (or anyone's) circuits.  May I have you run some simulations on your circuits first with a square wave input and then secondly a repeating plus, zero, minus, zero (tri-level) waveform?  The load voltage waveforms should be interesting, especially for the non-bridge designs.

Thx & cheers,

--- End quote ---

What software did you use?

A square wave, with a decent rise/fall time, will always cause clipping with an inductive load because a very high voltage will be required to achieve such a high di/dt.


--- Quote from: imo on November 18, 2018, 08:32:40 am ---
--- Quote from: Hero999 on November 17, 2018, 10:06:34 pm ---
--- Quote from: imo on November 17, 2018, 10:30:37 am ---This gives you nice swing (here aprox 45Vpp) on the output.
The Load is L1=3.5H with R6=5ohm in series (no idea what is the Resistance of your actuator).
Current +/-102.4mA into the Load based on input (here 2.048Vpp sine w/ DC offset +1.024V).
Not easy to simulate, however..
Mind it is a simulation only..
Needs some elaboration with R values and final components of choice..
You may add decoupling, output protection diodes, snubbers, etc. (you mess with inductive load)  :)

--- End quote ---
That circuit doesn't give a voltage offset of 1.024V, but a current offset of 102.4mA.

--- End quote ---
Nope, it is not about an output offset, but DC offset of the input signal generator used in my simulation:

--- Quote ---Current +/-102.4mA into the Load based on input (here 2.048Vpp sine w/ DC offset +1.024V).
--- End quote ---
The OP has got 2 sources at two inputs:
1. a constant 1.024V DC, and
2. the input from a DAC - 0..2.048V (=1.024 + 2.048*sin(x)).
Therefore my simulation follows his setup..


--- End quote ---
Oh I see what you mean, but the input is differential, so it really doesn't matter. Whether the negative input is set to 0V and the input swings from -1.024 to +1.024, or the negative input is set to +1.024V and the input swings from 0V to 2.048V, is immaterial. The output voltage will be the same and fortunately the DC bias voltages on the op-amp inputs will be within the common mode range.

I'm surprised you missed the error I made when simulating your circuit: I set the input voltage too high. I think the signal generator on your circuit shows thevoltage swing, but LTSpice uses the peak voltage, so I set it to double what it should be, causing clipping. I did realise after I uploaded the attachment, but decided not to redo it, in the hope you'd notice.
iMo:
Fixed above:

--- Quote ---The OP has got 2 sources at two inputs:
1. a constant +1.024V DC, and
2. the input from a DAC -> 0..+2.048V (=1.024 + 1.024*sin(x), in my simulation).
Therefore my simulation follows his setup..
--- End quote ---
OP - original poster, opamp - a device :)
iMo:
35y back I messed with a 5 pins chip called TDA2030 - a 14W/36V audio amplifier, basically a power opamp.. Here is the datasheet, pretty obsolete today, but may be there is something newer available today..
iMo:

--- Quote from: duak on November 18, 2018, 03:24:28 am ---I'm not able to simulate yours (or anyone's) circuits. 

--- End quote ---
I've just reinstalled my LTSpice to the latest and the Hero's .asc (double click on it) simulates..
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