Why is Vcc of the op-amp -9 to +9?

Question/Problem: Why is Vcc of the op-amp -9 to +9 in the FlexiForce sample circuit?

Answer/Solution: The Vcc and Vee of the Op-Amp used in the FlexiForce sample circuit was chosen as +9V and -9V respectively for several reasons.

1. The availability of +/-9V power supplies or batteries.
   
   
2. The op-amp's output can swing to within 1.3V of the supply rails.  This gives an output voltage of +/- 7.7V.  If the output is driven above this range, the op-amp will saturate.
   
   
3. The circuit was set up to give a 0 to 5V output when the feedback is adjusted to match the sensor resistance at maximum pressure used.  Therefore, having a range much greater than +/- 5V is not needed.  NOTE: If a wider range is required, the op-amp power supply can be increased up to the maximum allowed on the op-amp datasheet.

Tekscan, Inc.
307 West First Street. South Boston, MA. 02127-1309. USA
tel: 800.248.3669 / 617.464.4500 fax: 617.464.4266
marketing@tekscan.com


Print Page