Calculators » Electronic Component » 555 Astable Multivibrator Calculator: Frequency & Duty Cycle

555 Astable Multivibrator Calculator: Frequency & Duty Cycle

555 timer astable multivibrator frequency duty cycle calculator

This page provides calculators for determining the frequency and duty cycle of a 555 astable multivibrator. It also covers the formulas used in these calculations, employing two different methods.

555 Astable Multivibrator Calculator - 1

Inputs

Outputs

This calculator uses the resistor values (R1 and R2) and the capacitor value (C) as inputs to calculate the frequency and duty cycle of the 555 astable multivibrator.

Inputs: R1, R2, C

Outputs: Frequency, Duty Cycle

Example:

INPUTS: R1 = 10 kΩ, R2 = 10 kΩ, C = 0.220 µF (220 nF)

OUTPUT: Frequency = 218.1818 Hz, Duty cycle (%) = 66.67%, t HIGH = 0.003049 Sec, t LOW = 0.001524 Sec

555 timer astable configuration

Figure 1: Pin diagram of 555 IC used as astable multivibrator.

The following formula is used for the frequency and duty cycle calculation:

astable multivibrator formula1

555 Astable Multivibrator Calculator - 2

Inputs

Outputs

This calculator uses the desired frequency, duty cycle, and capacitor value (C) as inputs to calculate the required resistor values (R1 and R2).

Inputs: Frequency, Duty Cycle, C

Outputs: R1, R2

Example:

INPUTS: Frequency = 218 Hz, Duty Cycle = 0.60, C = 0.220 µF

OUTPUT: R1 = 6 kΩ, R2 = 12 kΩ

The following formula is used for the resistor calculation:

astable multivibrator formula2

Astable Multivibrator Calculator - 3 (using NOT Gates)

Inputs

Outputs

This calculator determines the frequency and time period of an astable multivibrator built using NOT gates or inverter gates.

Inputs: Number of NOT gates, Propagation delay of each gate

Outputs: Time period, Frequency

Example:

Inputs: Number of gates = 3, Propagation delay of each gate = 1 ns

Outputs: Time period of square wave = 6 ns (6.0 x 10-9 s), Frequency of square wave = 166,666,666 Hz (166.666666 MHz)

astable multivibrator using NOT gates or inverter gates

Figure: Bistable and astable multivibrator (AMV) made using NOT gates (i.e., inverter gates).

The following formula is used to calculate the frequency and time period:

Time period of AMV, T = 2 * n * tpd

Where:

  • n = Number of inverter gates or NOT gates
  • tpd = Propagation delay time of each inverter
  • T = Time period of square wave generated by AMV or ring oscillator.

Frequency of AMV (f) = 1/T = 1 / (2 * n * tpd)