Low-Cost Buffered Voltage Reference Circuit

Figure 1.  Low-Cost 5-V Reference Circuit Diagram

This is a low-cost voltage reference circuit.  Its main component is a general-purpose operational amplifier, the 741, configured to output a buffered fixed reference voltage for use by other IC's or circuits, such as an Analog-to-Digital Converter (ADC). 

The reference circuit above is designed to output 5 volts, and employs an AD589 as the 741's own reference.  The AD589 is a low-cost, temperature-compensated bandgap voltage reference that provides a constant output of 1.23 V.  Thus, the voltage at both inputs of the 741 is 1.23 V, which is also the voltage at the junction of the 1K and 3K resistors connected to the inverting input. This forces the 741 to output a steady voltage of approximately 5V (1.23V x 4K/1K = 4.92V).