5 VOLT REFERENCE CALIBRATOR
01/AUGUST/2004
This is a circuit to provide 5 volts with a precision regulator to calibrate multimeters. The circuit employs a 78L05 and a REF195(X) precision micropower low dropout voltage reference IC. The circuit supplies 5 Volts ±5 mV when using a REF195F.
COMPONENTS:
C1 1uF, 10V
C2, C4, C5 10 uF 6.3V eletrolytic or tantalum
C3, C6 .1 uF 50V ceramic disc
D1 1N4148
R1 8.2 ohms (used as a jumper wire, can be eliminated)
HOW IT WORKS :
The 9 volt voltage from a battery is reduced and regulated to 5.6 V with the 78L05 voltage regulator IC. The ground terminal is lifted from the circuit ground with 0.6 V from a diode PN barrier. The output, 5.6 V, feeds the precision regulator, and 5 V appears at the output terminal.
The REF195 is a precision micropower low dropout voltage reference IC. Each unit is individually adjusted at the factory. The letter that comes after the identifier indicates the tolerance: REF195E is a 2± mV output tolerance device. REF195F is ±5 mV and REF195G is ±10 mV. I bought a SOIC version unit from Digi-Key. A DIP version is also available.
The maximum output current is 30 mA, short-circuit protected. Complete specifications can be found on the Analog Devices home page in a PDF datasheet.
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