LF347: Lowest Positive Voltage on noninverting pin

Hi Dillon,

You're likely running into an output swing limitation issue but we will be able to better help you if you can provide a schematic, some detail on your input signal, and what type of load you're driving.

Take a look at the TI Precision Labs video on output swing for a better understanding of this topic (training.ti.com/ti-precision-labs-op-amps-input-and-output-limitations-1. The LF347 can only go to +/-13.5V on +/-15V supply, so I'm not surprised that you can't achieve what you're looking for as stated.

If you need to get closer to 0, I would recommend looking at an amplifier that is rail to rail output. If you're using low voltage supplies, the TLV9002 would be worth a look. Otherwise, we can give you some further recommendations once we better understand your application.

Thanks,
Paul

Thanks for the reference it was very useful. So if I'm using 5VDC+ on the V+ and OVDC on the V- then according to the datasheet, " VCM Common-mode: VCC– + 4 VCC+ – 4 V", my input range should be from Min: 4VDC Max: 1VDC, which doesn't look right :\. ???

So the idea of the circuit below is I'm creating a PWM and using a RC filter to turn it into an analog signal which seems to work but I can only get to 2.6VDC Max using this method. So I'm trying to use an OpAmp to increase my max to 3.14VDC Max which works fine but I'm unable to decrease to 0VDC on my minimum. The output from the opAmp will be going into another board that usually takes a voltage from a potentiometer.

Thanks for the help.

Hi Dillon,

the LF347 is a dino OPamp and needs a minimum supply voltage is +/5V. The allowed common mode input voltage range is -1V...+1V then.

The LF347 will not work properly with a 5V single supply.

Kai

Okay I'll give that a shot. Thanks.