Projects › Projects › Problem of Celsius and Fahrenheit scale digital thermometer using 8051 microcontroller (AT89C51) › Your teacher is right ! The
May 19, 2012 at 6:15 pm #7857
Your teacher is right ! The internal gain of pin 9 of 0804 is 2. But somewhere in the datasheet I found that “voltage below 2.5 can be applied to pin 9″.
To get a reference voltage of exact 5V, all you have to do is to leave the pin 9 unconnected.
Sample circuits found in the datasheet also do it this way!