Analog Design

Temperature Sensors like Thermocouples need cold junction compensation as a part of front end signal conditioning, this is done at the terminal block where the Thermocouple wires are terminated. This design has to be more accurate and broad, if the design we make has to work well in both Tropical and Temperate Climate Zones.

Another Method using a Copper Resistor

CA3140 and CA3130 are originally RCA part numbers( i feel). They are amazing close to ideal opamps, the input offset has to be trimmed. I used to use it when high input impedance is required. 1.5T ohm 10pA is the specs. A Electrometer can be made with just one opamp.

CA3130 has the additional Merit of swinging to the rails, if you are on a +/- 12V supply, the output will be +/-12V. This is a feature required in control applications.nn

CA3140 -4.5MHz, BiMOS Operational Amplifier with MOSFET Input/Bipolar Output

The LF198/LF298/LF398  are monolithic sample-and-hold circuits which utilize BI-FET technology to obtain ultra-high dc accuracy with fast acquisition of signal and low droop rate.

Operating as a unity gain follower, dc gain accuracy is 0.002% typical and acquisition time is as low as 6 µs to 0.01%. A bipolar input stage is used to achieve low offset voltage and wide bandwidth. Input offset adjust is accomplished with a single pin, and does not degrade input offset drift.

These devices are low cost, high speed, dual JFET input operational amplifiers with an internally trimmed input offset voltage. They require low supply current yet maintain a large gain bandwidth product and fast slew rate. In addition, well matched high voltage JFET input devices provide very low input bias and offset currents.

LF353 - Wide Bandwidth Dual JFET Input Operational Amplifier