Specifications

t.
Record the frequency where the X l0 Gain -3
dB amplitude is obtained in the Test Record
as ’measured -3 dB Frequency at X l 0 Gain’.
u. CHECK -- That the frequency is > l0 MHz.
v.
Divide the 0.35 by the-3 dB frequency
recorded in step 4-t. The result is the
’Calculated Rise Time at Xl 0 Gain’. Record
the result in the Test Record.
5. Check XI00 and X1000 Bandwidth.
a. Continue with the same set up as in step 4.
b. Set the sine wave generator frequency to 50
kHz and an amplitude of approximately 30
mVp-p.
c. Set the 1820/1822 GAIN to XI00.
d. Adjust the amplitude of the sine wave
generator for a waveform amplitude of
exactly 6 divisions on the oscilloscope.
e. Set the sine wave generator output frequency
to 500 kHz. Be careful not to alter the output
amplitude.
NOTE
The displayed waveform will be compressed in time to
form a solid rectangle. It is not necessary to alter the
time/div setting as long as the peak amplitude can be
measured
f. Slowly increase the output frequency of the
sine wave generator until the displayed
amplitude decreases to exactly 4.2 divisions.
This is a 3 dB reduction in amplitude.
g. Record the frequency where the -3 dB
amplitude is obtained in the Test Record as
’Measured-3 dB Frequency at X100 Gain’.
h.
CHECK -- That the frequency is > 2.5 MHz.
i. Insert a + 10 attenuator between the sine wave
generator cable and the 50 f~ termination.
j.
Set the sine wave generator frequency to 50
kHz.
k.
Set the ! 820/1822 GAIN to XIO00.
1. Adjust the amplitude of the sine wave
generator for a waveform amplitude of
exactly 6 divisions on the oscilloscope.
m. Set the sine wave generator output frequency
to 500 kHz. Be careful not to alter the output
amplitude.
4-7
182011822 Operator’s Manual
n. Slowly increase the output frequency of the
sine wave generator until the displayed
amplitude decreases to exactly 4.2 divisions.
This is a 3 dB reduction in amplitude.
o. Record the frequency where the -3 dB
amplitude is obtained in the Test Record as
’Measured-3 dB Frequency at XI000 Gain’.
p. CHECK -- That the frequency is > 1 MHz.
6. Check High Frequency CMRR.
NOTE
Common Mode Rejection Ratio (CMRR) is defined
the Differential Mode Gain divided by the Common
Mode Gain (normalized inverse of the Common Mode
Feedthrough). At higher frequencies where the
bandwidth of the amplifier begins to attenuate the
differential mode signal, both the differential mode gain
and the common mode feedthrough must be measured to
derive the CMRR.
a. Make the set-up the same as used for the
bandwidth tests (Steps 4-a through e).
b. Connect a BNC cable from the Frequency
Reference Signal Output of the high
amplitude sine wave generator to the External
Trigger Input connector of the oscilloscope.
(If the sine wave generator does not have
Frequency Reference Signal Output, insert a
BNC Tee adapter into the Output connector
and attach the external Trigger BNC cable to
the BNC Tee adapter.
c. Set the 1820/1822 GAIN to xl,
ATTENUATION to +1, INPUT
RESISTANCE to 1 Mr), BANDWIDTH to
FULL, +INPUT to DC, -INPUT to OFF.
d. Set the leveled sine wave generator output
frequency to 50 kHz. If necessary, adjust the
output amplitude for a display of exactly 6
divisions (300 mVp-p).
e. Without changing the output amplitude set the
output frequency to 1 MHz.
f. Measure the peak to peak output amplitude of
the 1820/1822. Record the answer as
’Amplifier Output Amplitude at 1 MHz’ to
two digit resolution (xx0 mV) in the Test
Record.
g. Divide the measured output amplitude by 300
mV. Record the answer to two digit
resolution (0.xx) as ’Differential Mode Gain
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