Universal Voltage Reference

Universal Voltage Reference

“This universal voltage reference circuit”- can provide a reference voltage that is continuously adjustable between -10V and +10V. If a REF02 is substituted for the  REF102 shown here, the output range will be -5V to +5V.The circuit uses both an op amp inverting gain path and a non- inverting  gain path simultaneously.  A potentiometer controls the ratio of these two gain paths. With the potentiometer wiper arm grounded,  U1 operates as an ordinary inverting amplifier with a gain of -1V/V. When the wiper arm is rotated to the other end of the potentiometer,  however, there is an additional gain path of +2V/V in addition to the -1V/V path. The resulting sum is a gain of +1V/V. At 50% rotation  (the wiper arm is exactly centered) the non- inverting gain path drops to +1V/V— cancelling the -1V/V gain entirely.  The output is then 0V. P1 should be a good quality potentiometer with high resolution and a good temperature coefficient.  Fortunately, the TC match of the resistance ratios of a potentiometer is much lower than its absolute resistance TC. (Circuit is created by Neil P. Albaugh  TI- Tucson)