Sound can be made using very few parts so many people think a buzzer is needed to make sound.
However, this circuit proves something different.
In this Simple Transistor Oscillator Speaker Circuit no buzzer is used.
Instead a small speaker is driven by transistors and therefore the circuit itself creates sound.
Moreover, it is very easy to build as a result the beginners can learn transistor working clearly.
Circuit Working:
Parts List:
| Components | Specification | Quantity |
|---|---|---|
| Resistors | 47k,1.2k ,120Ω | 1 each |
| Capacitors | Electrolytic 33µF 25V | 1 |
| Ceramic 0.047µF | 1 | |
| Semiconductors | Transistor BC547 NPN | 1 |
| Transistor BC557 PNP | 1 | |
| LED any color | 1 | |
| Speaker 8Ω or Small Speaker | 1 | |
| Power Supply 9V Battery | 1 |
First in this circuit the 9V power supply is applied.
Then capacitor C1 starts charging through R1.
After that transistor Q1 slowly turns ON and as a result current flows through LED1.
Next capacitor C2 sends feedback to transistor Q2 and then transistor Q2 switches ON and OFF quickly.
Because of this switching oscillations are produced and therefore the speaker vibrates.
And finally a buzzing sound is heard.
Also both transistors work together as a switching amplifier and thus the sound generation becomes stable.
Formulas with Calculation:
- The formula for charging time of capacitor C1
Time constant = R1 x C1
R1 is 47,000k
C1 is 33 microfarad
Time constant = 47000 x 33 x 10^-6
Time constant = 1.55 seconds
This delay helps in oscillation start.
2. Base current calculation for Q1:
Assume base voltage = 0.7V
R2 = 1.2k
Base current = 0.7 / 1200
Base current = 0.00058 amp
Base current = 0.58 mA
This current is enough to drive the transistor.
How to Build:
To build a Simple Transistor Oscillator Speaker Circuit follow the below connection steps
- So first we need to gather all the circuit parts.
- Transistor Q1 emitter pin is connected to ground through LED.
- Then its base pin connects to R1 and R2 resistors.
- After that collector pin go to Q2 base through resistor R3.
- Now, transistor Q2 emitter pin is connected to Vcc 9V.
- Meanwhile its base pin is connected with R3 and also collector of Q1.
- Then collector pin connects to one end of capacitor C2 and one end of speaker.
- Finally capacitor C1 positive terminal goes to Vcc 9V and negative terminal goes to GND.
Conclusion:
This Simple Transistor Oscillator Speaker Circuit is easy to build.
Here, the circuit uses few components and is good for students and beginners.
Furthermore it helps to understand transistor oscillation and therefore this circuit is ideal for basic electronics projects.