HP 8112A Operating, Programming And Servicing Manual page 228

Pre-Attenuator
Signal Output Amplifier
1 0.4-4 Servicing the Shaper and Output Amplifier
O l A
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
dB
0
dB
-4
dB
-24
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
circuit is given in Figure 10.4-3
+V
I a l b
( Q l A A N D 0 1 8 ARE
-
A MATCHED PA I R )
IsE
I BE
Figure 1 0.4-2. Current Mirror
K503 10
to
K502 1
&
K500 K501 0 . 1
101
settings. A simplified version of the
+V
O l B
to V
16
V
9.99
to V
0.99