[SOLVED] Pspice Instrumentation Amplifier Simulation

Hi,
Im trying to simulate an instrumentation amplifier (basic) in Pspice..

In my understanding the negative feed back causes the inverting terminal to achive the same voltage as the incoming signal..
So the differential voltage is developed across the Input resistors ( 1k , 1k series in this case) .This differential voltage is amplified and given to second stage..

My problem is that im triying to measure the differential voltage developed acorss the series resistors (1k ,1K) to find it only as around 150mV
The inputs given are 500mV & 200mV..So it should be 300mV ideally..
Checking the feed back terminals .. i found the U1 feed back terminal gives 350mV where it should only give 200mV...
Can somebody tell me what is the problem here??
Thanks & Regards

Just instead of 18 volt for supply, use +9 for positive port and -9 volt for negative ports of supply of the op-amps.

You should know that, each op-amp has certain common mode voltage range. When you use 18 and 0 for vdd, you can not use small voltages as a input voltages of the op-amp. Just refer to inside of the op-amp and you can easily can find that input transistors of op-amp need a min voltage for correct operation.

Using rail-to-rail OPs isn't enough to make this circuit work with input voltages near ground. As you can easily see, the present conditions would require the upper OP to generate a negative output voltage (of -0.4 V exactly), which isn't possibe with single supply. Using a dual supply is the most easy solution.

Thank you guys it solved my problem