Simple Frequency Divider using one transistor BC549

If you are looking for a simple frequency divider circuit. This circuit may be suitable for you.

It is designed to divide a frequency of input signal into just half.

Then, it goes out of the output.

The advantage of this circuit is a small circuit. It uses just a transistor only and other few components.

So cheap and get easily all components.

How does it work

frequency divider using transistor

Since the transistor-Q1 (BC549) gets a biased current in non-active status. So, It is active only in the range of input is positive voltage only.

This circuit uses a main idea from the common-base Colpitts oscillator model. The Colpitts circuit looks like other LC oscillators.

The simple circuit consists of a bipolar transistor with its output connected to the input, in a feedback loop. Which contain a parallel LC circuit.

The parallel LC circuit is called a tank circuit.

The tank circuit consists of L1, C4, and C5. They can set the frequency is about 16.5 kHz.

When input single of 30kHz-60kHz comes to the input of the circuit. The circuit will lock, generate the oscillator in a range frequency of 15kHz – 30kHz.

The other details, please see in the circuit. Good luck!

Parts you will need


  • Q1: BC549, 45V 100mA NPN Transistor
  • D1: 1N4148, 75V 150mA Diode

0.25W Resistors, tolerance: 5%

  • R1: 220K
  • R2: 68K
  • R3: 3K
  • R4: 5K

Ceramic Capacitors

  • C1,C4: 680pF 50V
  • C2: 0.001µF 50V
  • C3: 0.22µF 50V
  • C5: 0.039µF 50V
  • C6: 0.022µF 50V

L1: 33µH coil


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