Ac Gain - Stanford Research Systems SIM954 Operation And Service Manual

2.2 AC Characteristics

2.2.2 AC Gain

SIM954 300 MHz Dual Inverting Driver Amplifier
1.8
1.7
1.6
1.5
1.4
1.3
1.2
1.1
1.0
0
10
Figure 2.2: Typical SIM954 input VSWR
If optimal response at the end of an electrically long cable driven by
a nonideal source is of importance, an input attenuator can be used
to optimize the amplifier's input impedance near the upper end of
its frequency range. By trading gain flatness against absolute gain,
satisfactory results can usually be achieved even with electrically
long cables.
The typical AC gain is very flat up to about 10 MHz and will exhibit
variations of 0 2 dB up to 100 MHz. Beyond 100 MHz the gain will
slightly peak ( 1 dB or 12% in amplitude). Beyond the peak it will
fall o and reach its 3 dB point at about 300 MHz.
These gain variations depend on the internal compensation of the
op-amps (which are production lot dependent) and the tolerances of
the gain setting resistors in the SIM954 . Since the THS3091 op-amps
used in this module are transimpedance types, the gain peaking and
the 3 dB point are controlled by the feedback resistor.
The curves shown are based on a randomly chosen SIM954 prototype
and are characteristic for the product. However, SRS does not test
for the worst gain variation with a precision that resembles the plots
1
10 10
Frequency [MHz]
2 – 5
2