ITT - Index of

APPLICATION NOTES
FOUR-LAYER DIODE
Voc
Figure 13
RI
Figure 11
~----If----+B
01 02
A-Stable Circuit
YOC is greater than Y. of both diodes in
Figure 11. When power is applied, one of the
diodes will conduct. Let it be assumed that DI
flres flnt. Point A will go approximately to
ground potential and the current through RI
will be greater than Ih. The capacitor C will
begin to charge through R2 and DI to ground.
When the voltage at B exceeds the breakdown
potential of D2, it will conduct and point B will
go to ground. Since the capacitor can not
charge instantly, point A will drop approximately
Y. volts. This puts a negative voltage
at A, which if kept there until the turn OFF
potential of DI is reached, will prevent it from
sWitching back until the voltage at A reaches
Y._ C therefore charges through RI. The circuit
oscillates back and forth from DI to D2 with the
frequency dependent On RI C and R2C and on
YOC and the switching voltage of the diodes.
RI
voc
R2
C2
o-jf-+-...... -+!...j!-------.
1J
A modiflcotion of the gate circuit where both'
diodes are in the OFF state until a pulse is
opplied is shown in Figure 13. The Y. of DI is
slightly higher than YoC. A pulse of currenl is
opplied through RL which turns Dl ON. C2
charges through Dl ond R2 to Yoc- Cl charges
through Rl and Dl toward YoC olso_ When the
voltage at point A reaches Y. of D2, it will commence
to conduct. The voltage rise. at' B is
commutated back to DI, turning it OFF, which in
turn, turns OFF D2.
01 02
B
Figure 12
(-0
1f
Monostable Multivibrator
If diode Dl in Figure 12 is selected so that
it. switching voltage is less than Yoc, and diode
D2's is greater than YOC, diode Dl will normally
be in the ON condition and D2 will be OFF.
Capacitor Cwill charge through R2_ When D2 is
pulsed ON, DI will turn OFF due to the commutating
action of C. The voltage at point A
will then start rising as C charges through Rl
and D2_ When the voltage at point A reaches
the switchover voltage of Dl it will turn ON ond
D2will turn OFF until another p.ulse is received.
Frequency is determined by Rl C, YoC, and Y.·of
diode Dl.
1f
Figur'e 14
BI-Stable Multivlbrator Flip-Flop
The Y. of both diodes are chosen 50 that
they are greater than YOC in Figure 14. Whichever
diode is ON, it remains in that condition
until a trigger pulse arrives turning OFF the
diode which was ON and turning ON the previously
OFF diode by the commutating action
of C.
By interchanging one 4-layer diode with
its series cathode diode,-the circuit will become
sensitive to the polarity of the pulses. The
circuit will then switchover only when·. the
polarity of the trigger pulse reverses. This is
shown in Figure 15. Diode 1 triggers On negative·pulses
only and diode 2 on positive pulses.
Th.erefore, a positive pulse keeps branch B ON
and a negative pulse keeps branch A ON.
15-10