Tektronix 5441 Instruction Manual page 40

Theory of Operation-5441lR5441
HORIZONTAL AMPLIFIER
The horizontal amplifier amplifies the push-pull horizontal
Output Amplifier
deflection signal from the interface circuit board and applies
it to the horizontal deflection dates of the crt.
Transistors (2240-Q244-Q250 and Q270-(2274-Q280 are
connected as two separate current-driven feedback amplifi-
lnput Amplifier
The horizontal signal from the interface circuit board is
connected to the bases of Q200 and Q215. Under no-signal
conditions, the bases of Q200 and Q215 are within 150 mV
of ground. Resistive network R205-R207-R210-R212-R213,
between the emitters of Q20 and Q215, controls the emitter
degeneration of this stage. R212 provides a means of ad-
justing the emitter degeneration of the input amplifier and
thereby controls the gain of the horizontal amplifier, within
+
10%.
To compress an off-screen display so that it may be
viewed on the crt, the BEAM FINDER switch reduces the
dynamic range of the input amplifier. This is done by discon-
necting CR208 in the emitter circuitry of (2200-(2215, and
supplying a reduced current through current setting resis-
tors R205, R208, and R213.
Resistors R202 and R217 provide thermal compensation
for the input amplifier, while R222 provides a means of cor-
recting for differential unbalance in the amplifier or crt.
ers. lnput transistor Q240 (in the left output amplifier) is an
NPN transistor for better response to positive-going signals,
while input transistor Q270 (in the right output amplifier) is
an PNP transistor for better negative-going signal response.
Negative feedback is provided from the collectors of out-
put transistors Q244-(2250-(2274-Q280 to the base of input
transistors Q240 and Q270 through feedback networks
C242-R242 and C272-R272. Variable capacitors C242 and
C272 adjust the transient response of the feedback net-
works to provide good linearity at fast sweep rates. The
Zener diode-fast switching series diode, VR245 and CR242,
turn on when the sweep passes the right edge of the crt.
This action stops the collectors of the output transistors,
thus current limiting the output amplifier. Capacitors C240,
C250, and C280 are speed-up capacitors to improve the
amplifier response to fast changes. Diodes CR246 and
CR274 prevent Q244 and Q274 from going into saturation.
REV MAY 1982