741 non-inverting showing DC output

• 741 non-inverting showing DC output
  Posted by blinky87 on 13 Oct, 2019 11:42
• Hi all
  
  Playing around with a 741 Inverting opamp with this configuration;
  
  input voltage; 0.5V
  Rf = 2.1k
  Rin = 1k
  V+ = 9v
  V- = 0
  
  and the circuit works.
  
  However, in a non-inverting configuration, below, I have the following output;
  (I have tried different 741's)
  
  

  
  

• #1 Reply
  Posted by Andy Watson on 13 Oct, 2019 12:13
• The datasheet suggests that the common-mode input range of the 741 is two to three volts less that your power supply rails. In your case this would be between 2 and 7 volts (at best!). Having one input at 0.5V is not going to work - the 741 is not in its operating range. Similar restrictions apply to the output too.
  
  
  
• #2 Reply
  Posted by MarkF on 13 Oct, 2019 12:15
• +1 what Andy said.  The signal inputs and output can not approach the power rails.
  
  Offset Null:
  
  

  ---

  
• #3 Reply
  Posted by MarkF on 13 Oct, 2019 12:24
• #4 Reply
  Posted by blinky87 on 13 Oct, 2019 12:30
• Thank you guys. A lot of help here!
• #5 Reply
  Posted by blinky87 on 13 Oct, 2019 13:32
• I got the circuit working, thank you guys. Seeing the clamping in the video helped and confirmed my thoughts as well as your help.
  Also since it was single supply VCC+ 9V and VCC- was 0, clearly I had huge clamping and looked like half wave rectification.
  Putting VCC+/- 9  worked.