We found this amplifier with 50 MΩ input resistance in the May 1989 Radio Electronics magazine. The amplifier requires a dual power supply. The sum of R2 and R3 must be equal to R1.

We found this amplifier with 50 MΩ input resistance in the May 1989 Radio Electronics magazine. The amplifier requires a dual power supply. The sum of R2 and R3 must be equal to R1.