Tektronix 453 User Manual

Circuit Description-Type 453/R453
From Q63,
SW2308
!TRIGGER I
I
Ch 1 Vertical ---~r
Preamp
From Q284,
Vertical
Switching
NORM
R402p [;TI
R404
+150V
Internal
trigger
signal
to
A Trigger
Generator
Internal
trigger
signal
to
8 Trigger
Generator
L~
--8-4_0_0 _________ • 8401
§JJ [fill
(A Triggering I ( 8 Triggering I
_ CH 1 ONLY
Fig.
3-7. Trigger Preamp detailed block diagram.
Amplifier Circuitry
The internal trigger signal selected by the TRIGGER switch
is connected to the base of Q404. Transistor Q404 converts
the trigger voltage signal
at its base to a current drive for
the remainder of the Trigger Preamp. 0408
in the emitter
circuit of Q404 provides thermal compensation for the
amplifier.
The signal current at the collector of Q404 is connected to
the base of Q414. Q413, Q414 and Q423 are connected as
a current driven, voltage output operational amplifier.
The
amplified signal at the collector of Q414 is connected directly
to the base of Q413, and to the base of Q423 through zener
diode 0421.
This zener diode provides a DC voltage drop
while the signal
is connected to the base of Q423 with mini-
mum attenuation. Q413 and Q423 are connected as emitter
followers
in the complementary symmetry amplifier
4
con-
figuration.
This configuration overcomes the basic limitation
of emitter followers; inability to provide equal response
to
4
Lloyd P. Hunter, pp. 11-57-11-62.
3-10
both positive- and negative-going portions of a signal. This
is remedied in this configuration by using an NPN transistor
for one emitter follower, Q413, and a
PNP transistor for the
other emitter follower, Q423. Since Q413
is an NPN transis-
tor,
it responds best to positive-going signals and Q423,
being a
PNP transistor responds best to negative-going sig-
nals.
The result is a circuit which has equally fast response
to both positive- and negative-going trigger signals while
maintaining a
low output impedance. Feedback from the
output of the Trigger Preamp circuit
is connected to the base
of Q414 through
R419. This feedback provides more linear
operation. Total overall gain of the Trigger Preamp
is
about 10. The amplified internal trigger signal is connected
to the A and B
SOURCE switches through R427 and R429.
A TRIGGER GENERATOR
General
The A Trigger Generator circuit produces trigger pulses
to start the A Sweep Generator circuit. These trigger pulses
®

Tektronix 453 Specifications

General

Brand	Tektronix
Model	453
Category	Test Equipment
Language	English