Pre-Amplifier Unit; Vertical Pre-Amplifier; The Signal Splitter - Philips PM3055 Service Manual

5-1
PRE-AMPLIFIER UNIT
(A2)
The
pre-amplifier unit consists of:
-
Vertical pre-amplifier
-
MTB trigger pre-amplifier
-
DTB trigger pre-amplifier
-
Pre-amplifier control,
incl.
CHOPPER oscillator.
All control pulses for
this unit are
generated by the
pre-amplifier
control circuit, via the
1
C
bus (see section
5.4).
5.1
VERTICAL PRE-AMPLIFIER
stage
I
STAGE
2
STAGE
3
cn
CH. A
INPUT
CURRENT
CH.B
/
INPUT
CURRENT
1
)
TO
DELAY LINE
MAT2115
860214
Figure 5.1
The three stages
of the
vertical pre-amplifier
The vertical pre-amplifier consists of three
stages.
The
s
ignal splitter (Q0205) receives its input
signal for channel
A
(B)
from the attenuator unit and copies this
signal into three
identical differential output current signals for:
-
Vertical channel (pin
7
and
10)
-
MTB triggering (pin
5
and 12), see
section 5.2.
-
DTB triggering (pin
4
and
13), see
section
5.3.
Stage
2
(000020) consists of two integrated circuits
D2201 and D2202
connected in
parallel
and serves as a
vertical channel switch.
The switch selection is
as follows:
A
B
TRIG VIEW
ADD
pin
D2201
D2202
pin
0
1
0
1
11
pin
10
0
0
1
0
Further,
all
possible
2, 3,
or
4
channel combinations are possible in
alternated or chopped display (see also
section 5.4).