1 – 2
Operation
1.1
Instrument Overview
The SIM910 is a voltage preamplifier with low input and output
noise. It provides selectable gain from 1 to 100 of a single ended or
true di
ff
erential signal. The amplifier runs from DC to 1 MHz, or can
be AC coupled with 16 mHz
−
3dB frequency. In addition, the input
BNC shields can be grounded or floated allowing the signal ground
to be referenced to a local or remote ground. An overload light
indicates when the input or output maximum voltage, or maximum
output current has been reached.
The amplifier settings can be controlled either by the front panel
buttons or the remote serial interface. Digital noise is eliminated by
only clocking the microprocessor when settings are being changed.
The complete amplifier configuration (i.e., gain settings, coupling,
etc.) is saved in non-volatile memory.
The front end amplifier of this instrument is protected with a pair of
100
Ω
resistors (R103 & R104). Note that the internal-grounding in-
put configuration grounds the amplifier inputs
after
these protection
resistors.
A block diagram of the amplifier is shown below in Figure 1.1.
A
B
INPUT
A / A-B
AC /
DC
SHIELD
FLOAT/GND
INPUT
GROUND
+
-
FRONT
END
PROGRAMMABLE
GAIN
Ω
50
OUTPUT
REAR
PANEL
OUT
INPUT
PROTECTION
Figure 1.1: The SIM910 block diagram.
1.2
Front Panel Operation
All SIM910 configurations can be specified either from the front
panel, or by commanding through the remote serial interface. The
front panel is shown below (Figure 1.2). The front panel contains the
SIM910
JFET Preamp
