A simple circuit that uses transistors to make a megaphone acts like an electronic amplifier.
It is designed to boost weak sounds from a microphone MIC so they can be loud enough to be heard through a loudspeaker.
You can find this kind of circuit in many places, like public speaking events, sports games, rallies and anywhere else where you need to make voices louder.
The Transistors Based Megaphone Circuit features two TIP32 transistors set up in a push-pull arrangement, which helps to amplify the sound effectively.
Also, you can easily power this circuit with a 12V battery or a 12V DC power supply.
Circuit Working:
Parts List:
| Component | Specification | Quantity |
|---|---|---|
| Potentiometer | 4.7k | 1 |
| Resistor | 4.7k 1/4 watt | 1 |
| Capacitor | ||
| Ceramic | 0.22µF | 1 |
| Semiconductors | ||
| Transistors | TIP32 | 2 |
| Electret Microphone | – | 1 |
| SPST Switch | – | 1 |
| Speaker | 4Ω | 1 |
| Battery | 12V | 1 |
In the above circuit diagram electret microphone is really important because it picks up sound waves and changes them into tiny electrical signals.
In this design Q1 TIP32 transistor works as a preamplifier.
It makes the weak signal from the microphone much stronger.
After that the stronger signal goes to Q2 another TIP32 transistor which acts as a power amplifier.
This boosts the signal even more so it can power the speaker.
The 4Ω speaker takes the amplified electrical signal and turns it back into sound waves creating a loud sound.
To help control the volume there is a variable resistor VR1, that lets users adjust how strong the amplifier is based on what they like.
Capacitor C1 it blocks DC and allows only the Mic frequency to reach the transistor base
Resistor R1 biases the Mics internal circuit.
The S1 switch controls the power for the whole circuit making it easy to turn it ON or OFF when needed.
This whole circuit runs on a 12V battery which not only makes it work but also makes it easy to carry around and use.
Formulas with Calculations:
Below are the formulas with calculations for Simple Transistors Based Megaphone Circuit:
Voltage Gain of Transistor Stage:
Av = β × (RL / RE)
where,
- Av is the voltage gain
- β is the current gain of the transistor which is around 25-100 for TIP32
- RL is the load resistance for speaker impedance which is 4Ω
- RE is the emitter resistance
Power Output Calculation:
P = V² / R
where,
- P is the power output in watts
- V is the output voltage of the amplifier
- R is the speaker impedance which is 4Ω
Assuming the output voltage swing is around 10V:
P = (10 × 10) / 4
P = 100 / 4
P = 25W
Current Draw from the Battery:
I = P / V
where,
- I is the current drawn in amperes
- P is the power output of 25W
- V is the supply voltage of 12V
I = 25 / 12
I = 2.08A
How to Build:
To build a Simple Transistors Based Megaphone Circuit following steps are needed to be followed to design your own circuit for connections:
- Gather all the components as mentioned in the above circuit diagram
- Connect the base of transistor Q1 to one end of electret MIC through capacitor C1 and other end of Mic connect to GND of the circuit
- Connect one end of resistor R1 between capacitor C1 and MIC and the other end of resistor connect to positive supply of the circuit.
- Connect the collector of transistor Q1 to collector of transistor Q2.
- Connect the emitter of transistor Q1 to transistor Q2 and positive supply of the circuit
- Connect the base of transistor Q1 and Q2 to center pin of VR1 pot.
- Connect the second pin of VR1 pot to one end of 4 ohms speaker and other end of speaker connect to collectors of transistor Q1 and Q2.
- Connect a S1 switch from positive supply of circuit to +12V battery and negative of 12V battery connect to GND.
Conclusion:
This Simple Transistors Based Megaphone Circuit is an easy and efficient way to make your voice louder for public announcements and small gatherings.
It uses TIP32 transistors arranged in a push-pull setup which helps amplify sound clearly without much distortion.
The circuit runs on a 12V battery, so you can take it anywhere and it is simple to put together.
The variable resistor lets you adjust the volume easily making it user friendly.