06-30-2015 03:51 PM
Hi , im trying to simulate a Level shifter circuit based on OP-AMP (LF351) , to get first impression of the design , it should be a single power supply , i've connected everything , and the ouput look like a DC , it not why im expected for , i think maybe i was wrnog with power supplies , but i dont know. The purpose of the design is to shift and attenuate the input signal from +/-5V to 0/3.3 V .
this is my circuit :
06-30-2015 05:54 PM
1. The LF351 is speciifed for power supplies from +/-5 V to +/-15 V. I am not surprised that the output is not active with a single 3.3 V supply.
2. The negative common mode input limit is 2-3 V above the negative power supply voltage. Your signal is outside that range for most of the cycle.
3. The output voltage swing is 1.5 to 3 V less than the power supply voltages in both the positive and negative directions.
4. Typically a level shifter circuit built from an op amp will use power supplies larger than the maximum of the input or the output voltage ranges to assure the common mode voltage limits are not exceeded.
Try increasing your popwer supply to +/-10 to +/-15 V.
Lynn
07-01-2015 12:55 AM
Thank you.
07-16-2015 07:50 AM
You are missing a DC divider between single rail to ride the AC on Vcc/2.
Are you sure the op-amp can run single supply?
07-16-2015 07:51 AM
And also blocking caps with my above statement to keep the DC contained to this circuit only.