Pre-Attenuator
+V
O l A
I a
-
lb
( Q l A AND 0 1 8 ARE
A MATCHED PAI R )
I BE
IsE
+V
O l B
Figure 1 0.4-2. Current Mirror
The pre-attenuator circuit is controlled by the microprocessor via
latch
U500.
Logic signals
K l - K4
control relays
K500 - K503
to
provide three levels of attenuation according to the range of output
voltage required.
Table 10.4-2. Pre-attenuator ranges
Attenuation Active Relay(s) Final Output Range
0
dB
K503
10
to
16
V
-4
dB
K502
1
to
9.99
V
-24
dB
K500
&
K501
0 . 1
to
0.99
V
Signal Output Amplifier
The output amplifier amplifies the signal received from the shaper
IC via the pre-attenuator and adds the required offset voltage as
dictated by the HIL and
101
settings.
A
simplified version of the
circuit is given in Figure
10.4-3
1 0.4-4 Servicing the Shaper and Output Amplifier
Summary of Contents for 8112A
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