Often, electronic systems are guaranteed to operate with any supply voltage, within a given VCC range. Testing these circuits requires a regulated voltage supply that can be automatically incremented, from a minimum to a certain maximum. This makes taking parametric measurements for the circuit-under-test (CUT) easier.
Such a circuit uses the ubiquitous 317 voltage regulator (see the figure). Output of the regulator is calculated by VOUT = 1.25 × (RADJ/240+1). The variable RADJ is constructed from a linearized p-channel JFET, which has its resistance controlled by the op amp's output.
The amplifier increases the output of the R-2R digital-to-analog converter (DAC). For the given circuit values, VOUT spans 10 to 15 V, with increments of about 0.3 V. Changing the gain of the noninverting op amp will adjust that range. Also, increasing the DAC's number of bits will grant finer resolution for VOUT.
Please refresh the page if you have trouble reading this text.
Search Electronic Design
Email Newsletter
Sponsored By:
Electronic Design UPDATE provides readers with late-breaking news, opinions from industry experts, and timely technology stories. It's a unique opportunity to get your product message in front of engineers, engineering managers, and corporate managers while they're reading about critical information online.
Reprints
