Electronic – Bad on output of Constant-Current source

constant-currentoperational-amplifierproteussimulationtransistors

What I'm trying to do?

I'm making a constant-current source based off an existing design. The specs of the existing design are:

Existing Design

The design is of a constant current source capable of outputting 4-20mA output current from an input voltage of 0-2V.

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The Problem

The problem is when physically making the circuit, the output of this circuit is stuck at 56mA irrespective of input.

I cannot find/contact the original author of the schematics to discuss the problem and its up to me to figure this out.

The simulations also show the same results as in reality:

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Simulation Findings

Input: Sinusoidal Wave of 0-2V peaks of frequency 1 per second
Output Current: Constant current of 56 mA
Output Voltage: 13.6474V with small ripples with amplitude in microvolts.

PMOSFET Info

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V(Gate)   : 23V
V(Source) : 14V
V(GS)     : 8V

Question

1) Where should I start looking for issues?
2) What is the name of the op-amp configuration being used in the second stage? I do know that the 
   first stage is a voltage follower.

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EDIT 1: Resolving whether PMOSFET Symbol is correct

I have inverted the MOSFET just in case and the result is a little better but still not close to expected. Don't know whether inverted helped or made it worse.

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Best Answer

Your circuit simulates fine in Circuit-Lab.

schematic

simulate this circuit – Schematic created using CircuitLab

The comment from vangelo on your question is also applicable - for 0V in you cannot get 4mA out with this circuit.
It's not a 0-2V to 4-20mA converter, it's a 0-2V to 0-20mA converter.

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