Instrument Overview; Front Panel Operation - Stanford Research Systems BJT SIM911 Operation And Service Manual

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1.1 Instrument Overview

The SIM911 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 erential signal. The ampliﬁer runs from DC to 1 MHz, or can

be AC coupled with 0.7 Hz 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

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.

Figure 1.1: The SIM911 block diagram.

All SIM911 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

Operation

SIM911 BJT Preamp

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