Ac Characteristics; Bandwidth; Slew Rate - Stanford Research Systems SIM983 Operation And Service Manual

2.3 AC Characteristics

2.3 AC Characteristics

2.3.1 Bandwidth

2.3.2 Slew rate

SIM983 Scaling Amplifier
their default values; after the calibration completes, these values are
restored.
Disconnect all inputs and outputs to the SIM983 while performing the au-
tocalibration. To calibrate, issue the command ACAL, or press the but-
ton [polarity] and one of [gain ] at the same time. The calibration
completes and the instrument is ready for operation within 2 sec-
onds. If autocalibration is unsuccessful, for example because an
external voltage (which cannot be nulled) is applied to the input, the
calibration parameters revert to their original values and the com-
mand LDDE? will return Code 1.
Autocalibration does not a ect gain accuracy.
The gain-bandwidth product (GBP) of the SIM983 is a measure of
its small-signal behavior, and depends on G Four gain ranges
correspond to four values of gain-bandwidth product, as speci-
fied in the table on Page vi. For G
bandwidth of the amplifier is f
f (G) f (G 1 00)
3 dB 3 dB
The gain-bandwidth product is determined by a compensation ca-
pacitor in the feedback path of the gain-stage amplifier. It is possible
to override the value of this capacitor, giving the instrument more
bandwidth. To do this, use the command BWTH. If the bandwidth
is altered in this way, the next front-panel button press will return
the bandwidth to the value appropriate for the current gain. Cy-
cling the power or performing an autocalibration will also return the
bandwidth to its default value for the gain.
If the bandwidth is set to a value other than its default, the amplifier may
exhibit slow settling, excessive ringing, or oscillations.
The small-signal settling time of the amplifier is a complex function
of its gain and its bandwidth.
The slew rate of an amplifier is a measure of its large-signal be-
havior. It is the maximum rate of change of the output voltage,
measured in V s. The slew rate (SR) determines the maximum undis-
torted AC signal that can be output; for a sine-wave output at a fre-
quency f the maximum peak-peak voltage is V
The SIM983 is designed to be able to output a full-range sine wave
at 1 MHz.
1 the 3 dB small-signal
GBP G For G
3 dB
V
max min
2 – 3
1
SR ( f )