This module is the general voltage amplifier (with manual control).
It is a differential voltage amplifier presenting its output voltage at the iso-amp-out of the slot it is located in. The input stage of the amplifier is formed by the gates of cmos FET-opamps, there are no terminating resistors added. Input impedance is very high (>10Gohm) also in "ac-coupling". As a consequence the input will slowly drift away when not connected, resulting in a overload signal at the corresponding iso-amp-out. This causes no damage to the circuit but the LED draws battery-current. To prevent this, when not in use, a short-circuit connector (lemo pin 2-3-4) can be placed on the input when not in use .
All functions including "coupling ac/dc" can safely be operated during a measurement as switching is done after the input stage.
As an option the ac/dc switch can be changed to ac/hpf/dc The hpf (highpassfilter, approx 1kHz) can be used to detect small switching steps on a large dc-sweep. The differentiating action of the hpf blocks the sweep and allows for higher gain settings.
input:
front: V-in (lemo, pin 4=+in pin 3=ground pin 2=-in)
output back:V-out (to iso-amp-out)
measure control panel:
Range: 1/10/100/1000/10.000 V/V switch: coupling ac/dc (option:ac/hpf/dc)
manual control only
specs:
Input noise voltage : 10nV/sqrtHz (at frequencies >100Hz)
1/F noise : 2uVpp from 0.1-10Hz
Input offset voltage: <20uV (gain >100)
Input noise current : 0.5fA/sqrtHz
Input bias current : <1pA
Bandwidth : 100kHz
Drift : <0.5uV/c
for low impedance samples the M2b (or M2d) gives lower voltage noise
(1/F noise is 0.05uVpp)