Original question:
RCV420: 4...20mA current loop to voltage converter with high precision
Part Number: TLV333
Hi I want to use TLV333 Op-Amp IC to convert 4-20mA to 0-3V. I have made a circuit In TINA TI but I am not able to understand how some of the circuit use a voltage refrenc at inverting terminal to get and output. How we can achive the offset.
Zeya,
The first step converts 4mA to 20mA to a voltage of 0.6V to 3V using 150 ohms.
The goal is 0 to 3V. That equation is VOUT = VIN * 1.25 - 0.75V ; unity gain doesn't do this.
The TINA circuit has this ideal result
| Summary result | 4mA | 20mA | Units |
| VIN | 0.6 | 3 | Volt |
| VOUT | 0.051 | 2.939 | Volt |
| VCM | 0.600 | 3.000 | Volt |
Why is 0V to 3V the request result?
0V is on the lower power supply rail. So 3mA and 4mA would read the same. Does accuracy matter? Performance changes with 3.3V supply value.
For an ideal 0V to 3V these values R1,R2,R3,3.3V give that result.
