Table of Contents
Advertisement
Chapter 4
Arb Operation
1 dB
Note:
Note:
Output Impedance
Note:
DAQArb 5411 User Manual
2 dB
4 dB
By attenuating the output signal, you keep the dynamic range of the
DAC; that is, you do not lose any bits from the digital representation of
the signal because the attenuation is done after the DAC and not
before it.
attenuation (in decibels) = –20 log
where,
V
= desired voltage level for the output signal
o
V
= input voltage level.
i
For the DAQArb 5411, V
unterminated load.
For example, to change the output level to ±2.5 V into a terminated
load, use the following formula:
Attenuation = –20*log
You can change the output attenuation at any time during waveform
generation.
As shown in Figure 4-17, before the signal reaches the output
connector, you can select the output impedance to be 50
the load impedance is 50
output attenuation of 0 dB), the output levels are ±5 V.
A load impedance of 50
required for applications such as testing video devices. If the load is a
very high input impedance load (~1 M ), you will see output levels up
to ±10 V.
You can change the output impedance at any time during waveform
generation.
8 dB
16 dB
Figure 4-19. Output Attenuation Chain
10
= ±5 V for terminated load and ±10 V for
i
(2.5/5) = 6.020 dB
10
and all the attenuators are off (that is, an
is used for most applications but 75
4-20
32 dB
(V
/V
)
o
i
or 75
© National Instruments Corporation
. If
is
Advertisement
Table of Contents
