Tektronix 2215, Инструкция по эксплуатации

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TRIGGER
The Trigger circ u it, shown on Diagram 4, is composed o f
the Internal and External Trigger A m p lifie rs, Source­
sw itching circu it, and Trigger Generator c ircu it. Included
in the Trigger Generator c irc u it is the A u to Trigger and
A u to Baseline c irc u itry and the T V Triggering c irc u itry .
Internal Trigger Amplifier
The Internal Trigger A m p lifie r converts the d iffe re n tia l
current in p u t fro m the Trigger P icko ff c irc u it to a zero-
referenced, single-ended o u tp u t fo r use by the A and
B Trigger Level Comparators. D ifferential signals fro m the
P ic k o ff A m p lifie r c irc u it are connected via R421 and R422
to common-base transistors U421E and U421D respectively.
Transistor U421C and R428 constitute an inverting-
feedback am plifier that converts U421D co lle cto r current
to a voltage at the collector o f U421C. This voltage is added
in phase w ith the voltage drop across R427 produced by
the signal current o f U421E. The resulting sum is a single-
ended voltage signal th a t is applied to the base o f em itter-
fo llo w e r U 421A. The e m itte r-fo llo w e r stage provides a
low-output-im pedance signal source th a t drives both the
X Y A m p lifie r {through R701) and the e m itte r-fo llo w e r
(U421B) and supplies the trigger signal to the A lternate
B Sweep c irc u itry . The o u tp u t signal fro m U421B is applied
to the Trigger Source Switching Diode c irc u it at the
cathode o f CR440 where it is available fo r selection as the
triggering signal.
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