NE555D Просмотр технического описания (PDF) - Tiger Electronic

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Компоненты Описание

производитель

NE555D

Single Timer

Tiger Electronic 

NE555N/NE555D

shows the linear ramp generating circuit and Figure 14 illustrates the generated linear ramp

waveforms.

In Figure 13, current source is created by PNP transistor Q1 and resistor R1, R2, and RE.

For example, if Vcc=15V, RE=20kΩ , R1=5kW, R2=10kΩ , and VBE=0.7V,

VE=0.7V+10V=10.7V

Ic=(15-10.7)/20k=0.215mA

When the trigger starts in a timer configured as shown in Figure 13, the current

flowing through capacitor C1 becomes a constant current generated by PNP transistor and

resistors.

Hence, the VC is a linear ramp function as shown in Figure 14. The gradient S of the

linear ramp function is defined as follows:

Here the Vp-p is the peak-to-peak voltage.

If the electric charge amount accumulated in the capacitor is divided by the

capacitance, the VC comes out as follows:

V=Q/C (15)

The above equation divided on both sides by T gives us

10/11

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