This amplifier for electrometer can work with currents of 0.1 pA in a band of 1 Hz. The circuit is from NASA in a publication of the 60s. Transistors are general purpose types.
The integrated circuit used in this configuration for noise reduction on FM radios is not common...
The presented circuit provides an output voltage proportional to the input current, according to...
The low-pass filter shown in the figure uses two operational amplifiers with JFET at the input to...