Digital Electronics - Flip-Flops - Discussion

Discussion Forum : Flip-Flops - General Questions (Q.No. 8)
8.
The timing network that sets the output frequency of a 555 astable circuit contains ________.
three external resistors are used
two external resistors and an external capacitor are used
an external resistor and two external capacitors are used
no external resistor or capacitor is required
Answer: Option
Explanation:
No answer description is available. Let's discuss.
Discussion:
4 comments Page 1 of 1.

Giri said:   8 years ago
Thanks @Pradeep.

Dhanalakshmi said:   8 years ago
To find Astable multivibrator output frequency.

Formula,
Output frequency = 1.44 / [ (R1+2R2)*C ].
So we need 2 external resistors and external capacitor.

Alamgir said:   9 years ago
I Agree with you @Pradeep.

Pradeep said:   1 decade ago
The above referenced astable circuit is Multivibrator. The astable multivibrator generates a square wave, the period.

Of which is determined by the circuit external to IC 555. The astable multivibrator does not require any external trigger to change the state of the output. Hence it is also known as free running oscillator. The time during which the output is either high or low is determined by the two resistors and a capacitor which are externally connected to the 555 timer.

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