Buffered Probe for Digital Voltmeter
Created: Oct 02, 2016
No description available.
In today’s world, digital voltmeters are widely used to measure potential difference. As time goes by, digital voltmeters have replaced analog voltmeters due to the some advantages associated with digital systems. The use of DVMs eliminates observational errors in measurement committed by the observers. Parallax errors, that are common in analog voltmeters, are entirely eliminated. Also, DVMs are versatile, accurate, compact, cheap, portable, and power-efficient. This reference design is a buffered probe designed for digital voltmeters. It utilizes the LTC6090 high voltage, high precision operational amplifier. The LTC6090 is unity gain stable and is internally protected against overtemperature conditions.
This design is powered with a +65V and -65V split supply through LT8300, which is a micropower high voltage isolated flyback converter. With input leakage current typically below 5pA, circuit loading is essentially negligible (<VOS) for source impedances approaching a GΩ. The useful full-swing frequency response is over 20kHz. In this design, the LTC6090 acts as an ordinary unity gain stable operational amplifier, so constructing an electrometer grade buffer stage is simply a matter of providing 100% feedback with the classic unity-gain circuit. No discrete FETs or floating biasing supplies are needed. The output stage may be turned off with the output disable pin (OD). By tying the OD pin to the thermal warning output (TFLAG), the part will disable the output stage when it is out of the safe operating area. These pins can easily be interfaced to any logic family.
Since the LTC6090 provides a unity stable gain, it is an ideal solution for a buffered output to a digital voltmeter. It enables simplified high impedance and/or large signal buffer and very wide dynamic range amplification solutions.