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Flip-Flops - Technical MCQs

Q1:

In a 555 timer, three 5 k resistors provide a trigger level of ________.

A 1/4 VCC and a threshold level 1/2 VCC

B
1/3 VCC and a threshold level 3/4 VCC

C
1/3 VCC and a threshold level 2/3 VCC

D
1/4 VCC and a threshold level 2/3 VCC

ANS:C -

1/3 VCC and a threshold level 2/3 VCC

The 555 timer IC is an amazingly simple yet versatile device. The IC is quiescent so long as the trigger input (pin 2) remains at +VCC.
The three resistors in the voltage divider all have the same value (5K in the bipolar).

This doesn't give us absolute values for "e" or "E," but it does give us the ratio e/E = 2/3.