This 1 MHz differential voltage amplifier combines low input voltage noise and low offset voltage drift. This combination is important for long-lasting measurements on samples at cryogenic temperatures. Commercial available amplifiers suffer from higher voltage noise or lower offset voltage stability over temperature and in time.
Low input voltage noise is reached by using a discrete dual J-FET (IF 3602) in the input stage. The offset voltage drift of this low noise J-FET input stage is reduced by a precise servo control-loop. The voltage gain can be switched between x100, x1'000, x10'000 and a variable LP-Filter (100 Hz... 1 MHz) is also integrated. At a gain of x100 an input differential voltage up to ±100 mV can be amplified linearly. The amplifier can be AC or DC coupled, the input resistance can be switches between 10 MOhm, 1 GOhm and infinite (DC-only) and the common-mode voltage can be up to ±1 V. All these features make the Low Noise / Low Drift Differential Amplifier a versatile laboratory preamplifier.