In the absence of a circuit for amplifying the signals of a thermocouple in a temperature control or other industrial application, the configuration shown in figure 1 may be an interesting solution.
The CA3140 consists of an operational amplifier with junction field effect transistors (JFETs) at the input, which gives it an extremely high input impedance. The gain of the circuit is given by the relationship between R3 and R1, and values of components that can be changed depending on the application.
Note that the power supply used does not need to be symmetrical, but should have excellent filtering given the high gain of the circuit. In figure 2 we have a suggestion of printed circuit board for the assembly of this application.
We also inform you that equivalent operational amplifiers such as the TL070 and TL080 series can be tried.
MATERIAL LIST
CI-1 - CA3140 - Operational Amplifier
R1, R2 - 100k ohm x 1/8 W - resistors - brown, black, yellow
R3, R4 - 1.5 M ohm x 1/8 W - resistors - brown, green, green
Several:
Printed circuit board, 12 V power supply, wires, solder, etc.
