Hi,

I designed a circuit as in the picture attached.

could you please tell me that the circuit is good or can be better?

 

Have you tried to simulate it?

 

Have you tried to simulate it?

No, I have not yet simulated it.

 

Once you do it, you will know if it could work or not (sorry - had to edit what my crappy keyboard sent when posting from my mobile)

Put some effort prior to asking here.

 

hi M,
Can you give more information about your project.?
It should be possible to simulate in LTSpice.
E

 

Once you do it, you Will the flash of it.

Put some effort prior to asking here.

In fact, I put some resistor and capacitor in the circuit by my thought for reliability.
The Diode to avoid mistake connection.
The resistor 2.2K and 100nF cap to avoid any spike voltage on CE of the transistor.
The 220pF cap for compensator.

 

hi M,
Can you give more information about your project.?
It should be possible to simulate in LTSpice.
E

Hi Eric,

I want to convert a voltage to 4-20 mA current, I know the circuit will work but I have not experience with this circuit and my question about is there a better circuit than my circuit?

 

hi M,
This clip is from a AD694 V2I converter IC.
It may give you some idea's
E
I will run your circuit in simulation.

 

hi M,
This is what LTS shows, what is the 4-20mA connected too.??

E

 

hi M,
This is what LTS shows, what is the 4-20mA connected too.??

E

Dear Eric,

I simulated the circuit by Circuit Maker and the results are as follow:

The output is the same that I wanted

 

hi M,
It is important to consider how this 4 to 20mA is going to be used by any equipment that is connected to it. It is connected to -9V.
Also your output current appears in the wrong sense,
ie: with -3V inp you get a 20mA current and at -0.6V its is 4mA,

You said in your first post -3V thru -0.6V for 4 to 20mA.

E

 

hi M,
It is important to consider how this 4 to 20mA is going to be used by any equipment that is connected to it. It is connected to -9V.
Also your output current appears in the wrong sense,
ie: with -3V inp you get a 20mA current and at -0.6V its is 4mA,

You said in your first post -3V thru -0.6V for 4 to 20mA.

E

Hi Eric,

OK, in fact, the power supply is a single 24 VDC and I need double power supply due to the op-amp, I produced double voltage from the power supply, the 4-20 mA current must enter to negative of 24VDC power supply.

I want to convert output DAC voltage from a microcontroller to 4-20 mA, after DAC I used an op-amp inverter to invert the voltage of DAC.

 

hi M,
This is another option, single supply 9v.

Have you simulated your latest version.?
E

Added an image with the Vout across load plotted.

 

hi M,
This is another option, single supply 9v.

Have you simulated your latest version.?
E

Hi Eric,

Your offer is better than my idea, thanks

 

hi M,
You have to choose a high enough supply voltage to drive the current output stage, its call compliance.
That means there must enough supply voltage to allow for the voltage drop across the Emitter resistor, transistor and 250R load resistance when passing 20mA thru the load resistance

With a 9V supply thats just possible, using a 12V supply will give some overhead to spare. [Compliance voltage]

E