ITT - Index of

APPLICATION NOTES FOUR-LAYER DIODE
CIRCUITS
Relaxation Oscillator
Figure 3 illustrates a circuit used far oscillator,
sweep generator, and timing applications.
The output is a saw-tooth voltage the amplitude
of which is dependent On the diode Ys• Frequency
is dependent upon the RlC time constant
and the supply voltage. The supply voltage
should be chosen so that the charging of C is
done in the linear portion of the curve. When C
reaches Ys the diode breaks down and conducts.
C rapidly discharges through the diode.
Rl should be large enough so that it will not
pass Ih or the diode will remain in the ON can·
dition after C has discharged. With C discharged
the diode turns OFF and C commences
to charge again. Rl must be able to pass the
switching current (Is) when C reaches Y, and
the diode flres again.
Jl o--j~, 0: 1 ,0 C . ..'_
'~lf
Voc
Triggered Pulse Generators
These circuits are used mainly for generating
ar amplifying pulses and for triggering purposes.
They are similar to Figure 3 except that
the switching voltage of the diode is greater
than the supply voltage. Four variations, with
their input and output pulses, are shown in
Figure 4. A pulse, large enough to break dawn
the diode, is capacitively coupled either positive
to the anod e or negative to the cathod e.
The conventional diode is used to present a
high impedance to the input pulse.
Voc
Figure 5
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R2
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L·C Pulse Generators
As with the circuits in foregoing section,
those in this section also require a pulse to flre
the diode. Y, of the diode is greater than the
supply voltage. In Figure 5, a negative pulse
is applied to the cathode which breaks down
the diode. C, which was charged to YoC
through R, discharges through the diode, L,
and Rl. This is a resonant circuit and the wave
shape across Rl is a half sinusoid. When the
current goes through zero, the voltage across
the diad e becomes negative, turning it 0 FF.
A smail positive output will occur due to the
pulse recovery current through the diad e.
Figure 6
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1[0---1
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15-8