Tektronix 434, Instruction Manual, Page: 45 / 222

C ir c u it D e s c rip tio n —4 3 4
C h a n n e l 1 D io d e G a te
C U R R E N T P A T H
R E V E R S E - B IA S E D D IO D E S
V e r tic a l
s ig n a l t o
D e la y - L in e
D r iv e r S tage
F ig . 3 -6 . E f f e c t o f D io d e G a te s o n s ig n a l p a th ( s im p lif ie d p a th ) . C o n d it io n s s h o w n f o r C H 2 m o d e o f o p e r a t io n .
e m itte r level o f Q 4 2 0 , and m o re n e g a tiv e ly (to w a rd th e
c o lle c to r level o f Q 4 3 5 th ro u g h R 4 2 8 , C R 4 3 2 and R 4 3 2 )
o n th e C R 4 2 8 side. T h is charge is sto re d w h ile Q 4 3 5 is o f f ,
and h o ld s th e e m itte r o f Q 4 2 5 m o re negative th a n th e
e m itte r o f Q 4 2 0 . W hen b o th Q 4 2 0 and Q 4 2 5 are o f f th e
vo lta g e a t th e ir bases becom es a p p ro x im a te ly e q u a l. W hen
Q 4 3 5 com es b a ck o n , th e tra n s is to r w it h th e m o s t negative
e m itte r w ill
s ta rt c o n d u c tin g fir s t, w ith th e re s u ltin g
negative m o v e m e n t a t its c o lle c to r h o ld in g th e o th e r tr a n ­
s is to r o ff . T h e c o n d itio n s d e scribed p re v io u s ly are reversed;
n o w th e C hannel 2 D io d e G ate is reverse biased, and th e
C hannel 1 signal passes th ro u g h th e C hannel 1 D io d e G ate.
C H O P . In th e C HO P m o d e o f o p e ra tio n , th e S w itc h in g
M u ltiv ib r a to r Stage fre e runs as an astable m u ltiv ib r a to r a t
3-8