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THEORY OF OPERATION
J'.he amplifier is dri";.ren
by
an input
transformer which provides for isolation
and matching functions in the primary
by
means of split windings and resistive
pads.
The input level control provides
a constant load to the input transformer
secondary while furnishing a gain con-
trol. function.
Transistor Ql operates
as an emitter follower and provides im-
pedance matching
fI
om the input to the
~ltage
amplifier, Q2.
Note that Q2 is
the only stage which has voltage gain.
A high frequency transistor is used at
this point to improve stability"
The
output stages of' the amplifier operate
Class B, ani
aI'8
arranged in the circuit
configuration known as
lIsingle
ended
push-pu.1.1
11
or a tlfollowed emitter
f
ollow-
erll.
The upper and lower units are in
series across the power supply, and the
load is connected at their junction"
When the signal at the collector of Q2
goes negativej Q3,
Q5,
and Q7 conduct;
since they are all PNP types"
When the
RI
C7
UNrnOE~R~SUIW------------
PRINTED BOARD
QI. _____ __
CIO _ _ _ _ _ _
+-_
R2
1 1 - - - -
4 --:
C9
signal goes positive; Q4-, Q6, and Q8
all~
conduct; since Q4- is an NPN type.
Th\
r'"
the full signal appears at the junction·
1
pOint.
Q3, Q5, Q7, and Q6, Q8 are con-
nected in a compound or !1Darlington
l1
conf'igUIation, a conne-:tion which provi-
des extremely high cUI'rent gain, and im-
proves linearity at high signal levels.
General feedback loops are employed in
the amplifier including R3, R19, 02, C4-,
and 05"
02 and C4- provide high frequency
feedback
whi~e
C5 sUPvlies positive feed-
back from the output to the collector
circuit of Q2 to increase the signal
handling capacity of this stage.
Thermistor R4 compensates for vaIiations
in the amplifier bias due to temperature
changes.
Choke Ll renders the amplifier
insensitive to changes in capacity across
the outpilt leads"
The power supply is a
conventional full wave b.ridge rectif ier
with filter capacitor circuit.
Q6
-------- Q7
T2
Fl
011
PARTS LOCATION
M6108 TRANSISTOR
MONITOR AMPLIFIER
-3-
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