it's the schematic.
there are some questions.
1、the schematic is right？
2、the voltage of VREF（pin7）can't reach 2.5V，only about 1V.【VCC=5V】
3、4 MOSFETs can be turned on only three.
4、the voltage of pin12 Doesn’t equal the Twenty times the second pin and the fourth pin of the voltage difference +1.5V。
...........
what should I do to solve these problem.
thanks to answer.
For a Chinese, English is really hard to ask questions
