M2b, Voltage measurement, low 1/F noiseThe module is now modified to have manual control on the front (ac/dc, gain 100...10k) This amplifier has a fixed 100x dc-gain and a postgain 1/10/100 V/V switchable ac/dc It can be used for very low-noise dc-measurements (50nVpp 1/F noise in 10 seconds). Noise at 1Hz is 30x lower compared to the general purpose amp M2/M2m (but drift and input current are higher). The design is based on a discrete dual JFET-input stage, care should be taken not to damage the input by overloading it (>1V can cause damage). The amplifier contains no chopper or oscillating circuits that could produce interference Noise compared to commercial low-noise differential FET-preamps 1/F Noise of M2b design (labelled "dcampft6") is at least 20x less specs: Input noise voltage: 2nV/sqrt Hz >10Hz (2.5nV/sqrtHz @1Hz !!) Input noise current: 5fA/sqrtHz Input bias current : <5pA Temp drift : <2uV/c Bandwidth : 200kHz..10kHz (gain=100..10K) Gain : 100/1k/10k V/V (on ac, 100/1k/10k dc-gain=100 fixed) |