3.6 Basic Operation Examples
CA5350
3-22
(Reference material)
About rise time
Rise time is defined as the time taken by output signal of
CA5350
to change from 10% to
90% of the amplitude of an ideal square-wave (rise time=0s) input signal.
出力電圧波形
t
100%
90%
10%
0%
立上時間
Figure 3-14 Definition of the rise time
Response of
CA5350
is affected by the rise time decided by filter as well as the response
time of I/V amplifiers. When the rise time of I/V amplifier is t
IV
and the rise time of
filter is t
FILT
, total rise time t
TOTAL
can be approximated with the following expression.
t
TOTAL
＝
t
IV2
＋
t
FILT2
Rise time of I/V amplifier takes the following values according to I/V GAIN settings
(supplementary values).
10G (10
10
) V/A
≒
25µs
1G (10
9
) V/A
≒
5µs
100M (10
8
) V/A
≒
2µs
10M (10
7
) V/A
≒
1µs
1M (10
6
) ~ 10k (10
4
) V/A
≒
0.7µs
When electrostatic capacitance of cables and sensor connected to current input terminal
(CURRENT INPUT)
becomes large, rise time of I/V amplifier will become large.
Larger (longer) is the rise time of I/V amplifier and filter, it will become closer to the
total rise time of
CA5350
.
Example 1) When gain of I/V amplifier is
10G V/A
(rise time
≒
25µs) and filter setting is
1µs,
t
TOTAL
＝
t
IV2
＋
t
FILT2
＝
(25
×
10
-6
)
2
＋
(1
×
10
-6
)
2
≒
25µs
Example 2) When gain of I/V amplifier is
10G V/A
(rise time
≒
25µs) and filter setting is
30µs,
t
TOTAL
＝
t
IV2
＋
t
FILT2
＝
(25
×
10
-6
)
2
＋
(30
×
10
-6
)
2
≒
39µs
Example 3) When gain of I/V amplifier is
10G V/A
(rise time
≒
25µs) and filter setting is
300µs,
t
TOTAL
＝
t
IV2
＋
t
FILT2
＝
(25
×
10
-6
)
2
＋
(300
×
10
-6
)
2
≒
301µs
Even if the time set for filter is shorter than the rise time of I/V amplifier,
responsiveness will not improve as mentioned above. Besides, noise will increase in high
frequency range. Make appropriate filter settings according to gain of I/V amplifier, and
response of the signal to be measures/detected.
Rise time
Output voltage waveform
