Floating Gates Offer Exquisitely Precise Control Of Comparator Thresholds

In research, test and measurement, and process control, signal conditioning for today's most sensitive analog sensors, detectors, and transducers must provide ultra-low-level input-signal detection, incredible resolution, and the least possible load on the signal source. But those characteristics are in short supply. Today's highest-end voltage comparator, the LM393A, has a 2-mV offset and draws 100-nA of bias current. A good specialty comparator can cut that bias current to 200 pA at the same offset.

Now, the ALD2321 comparator from Advanced Linear Devices exhibits only 0.20-mV offset and takes only 20 pA from the sensor. Taken together, that's a feather-touch that's 50,000 times lighter on the sensor. This breakthrough is based on the company's electrically programmable analog-device (EPAD) technology.

MOSFET transistors that have programmable threshold voltages can ultimately replace mechanical trim pots (see the figure). Once programmed, the set voltage and current levels are stored indefinitely inside the device, even with power removed. EPAD allows software-based analog-circuit trimming in as many as 100,000 discrete steps with resolutions as fine-grained as 0.1 mV.

List pricing for the ALD2321 is $1.78 to $2.69 in quantities of 100 units.