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.
These devices are now available with Intersil.
CA3140 -4.5MHz, BiMOS Operational Amplifier with MOSFET Input/Bipolar Output
The CA3140A and CA3140 BiMOS operational amplifiers feature gate protected MOSFET (PMOS) transistors in the input circuit to provide very high input impedance, very low input current, and high speed performance. The CA3140A and CA3140 operate at supply voltage from 4V to 36V (either single or dual supply).
A voltage regulator that uses CA3130 – Range 0.1 to 50V at 1 Amp.
CA3130 – 15MHz, BiMOS Operational Amplifier with MOSFET Input/CMOS Output
“15MHz, BiMOS Operational Amplifier with MOSFET Input/CMOS Output
A CMOS transistor-pair, capable of swinging the output voltage to within 10mV of either supply-voltage terminal (at very high values of load impedance), is employed as the output circuit.”
Applications – Ground-Referenced Single Supply Amplifiers, Fast Sample-Hold Amplifiers, Long-Duration Timers/Monostables.