This circuit of the 70's uses transistors of the time. The circuit can amplify signals from 10 Hz to 100 kHz and modern equivalent components can be used. The circuit is from Ferranti.
The Texas Instruments TPS7A92 integrated circuit consists of a low-voltage (LDO) linear voltage...
This circuit to increase the sensitivity of instruments to 100 uA (or close to it) was found in...
This voltage controlled oscillator uses a varicap to change the frequency. Usin a 100 turns coil...