I simulate the circuit but an error appear,such as Error: unknown subckt: xu4 0 0 0 +15v r9_1 u3_14 u3_14 u3_13 u3_13 r7_1 -15v 0 0 0 lm224j
Then I don't know how to correct the error,I don't understand the error ,I want there is some annotations so I can understand my mistakes.
Thank you!!