I'm designing an analog output that takes a 0-5volt from a DAC and uses an op amp to step it up to 0-10volt, then turns it into a 0-20ma signal with a XTR111 and can use a switch to output 0-10v or 0-20ma. I want to make sure everything looks good before I start my first prototype.

 

I seethe circuit but it is not clear just what connects to where.So I can't provide an answer.

 

I seethe circuit but it is not clear just what connects to where.So I can't provide an answer.

AO.24 = 24volts in from external PSU for loop power

AO1 = output from the dac 0-5v then op amp turns it into 0-10v

%OW0 = output to the field device

AO1com = 24volts com from external PSU

AO1.1 & AO1.2 = go to the dip switch to swap from 0-10v or 0-20ma

hopefully this helps

 

I want to make sure everything looks good before I start my first prototype.

Should be fine as it duplicates the design from the data sheet.

 

Q22 has two things wrong with it.
U14 LM321 does not work well the inputs and outputs near the supply rails. I did not study the circuit well, but you might look for a R-R opamp designed for input & output voltage at the supply.

Should be fine as it duplicates the design from the data sheet.

no it does not.

 

The input is only 5 volts with a gain of 2

 

The LM321, inputs do work at 0V but the output does not pull down well. The two 10K resistors are what is pulling down as you get below 0.7V. Just saying you have 20k pulling down when the OP gives up.

 

To the other question.

 

Q22 has two things wrong with it.

Good call!
Q22 is a pnp type transistor not a npn.

 

The LM321, inputs do work at 0V but the output does not pull down well. The two 10K resistors are what is pulling down as you get below 0.7V. Just saying you have 20k pulling down when the OP gives up.

The LM321 has the same input configuration as a LM358 and it works to zero volt input.
Only need to change Q22 to a pnp type like a 2N2907.

 

The LM321 has the same input configuration as a LM358 and it works to zero volt input.

The LM321, inputs do work at 0V but..................

 

But what?

 

But what?

but the output does not pull down well. The two 10K resistors are what is pulling down as you get below 0.7V. Just saying you have 20k pulling down when the OP gives up.

It works, don't change things. Just saying that amp dose not pull down well. The output structure fails below 0.7V.

 

It works, don't change things. Just saying that amp dose not pull down well. The output structure fails below 0.7V.

 

Thanks guys, I'll change Q22 to a BC557 and then send it off to prototype.