Question

In IC 555 timer, three \(5k\Omega\) internal resistors act as voltage divider, which provides bias voltage to the upper comparator and to the lower comparator in the order of (in \(V_{CC}\)).

• A. \[ \frac{2}{3},\frac{1}{3} \]
• B. \[ \frac{1}{3},\frac{1}{3} \]
• C. \[ \frac{1}{3},\frac{2}{3} \]
• D. \[ \frac{2}{5},\frac{1}{5} \]

Hint:

The trigger comparator of a 555 timer works at \[ \frac{1}{3}V_{CC} \] and the threshold comparator works at \[ \frac{2}{3}V_{CC}. \]

Answer 1

The Correct Option is A

Concept: The IC 555 timer contains three equal resistors of value \[ 5k\Omega \] connected internally in series. They divide the supply voltage into three equal parts.

Step 1: Determine the comparator reference levels.
The voltage divider produces two reference voltages: Upper comparator reference: \[ \frac{2}{3}V_{CC} \] Lower comparator reference: \[ \frac{1}{3}V_{CC} \]

Step 2: Match with the given options.
Therefore, \[ \boxed{ \frac{2}{3}V_{CC}, \frac{1}{3}V_{CC} } \] corresponds to option (A).