The TA7642 IC is a super sensitive chip designed for AM radio.
It needs just a few additional components and operates on low voltage, which makes it ideal for creating compact and efficient radio receivers.
In this article, we will look at a Simple AM Radio Receiver Circuit using IC TA7642.
We will describe the function of each part and provide simple instructions to help you assemble the circuit.
Note the IC TA7642 is a newer version of the MK484 chip, which itself is a newer version of the ZN414 that was widely used many years ago.
Both the TA7642 and MK484 chips come in a TO-92 case, giving them a similar appearance to a transistor.
Circuit Working:
Parts List:
| Component | Value/Type | Quantity |
|---|---|---|
| Resistors (1/4 Watt) | 1k | 2 |
| 100k | 2 | |
| 220Ω | 1 | |
| Capacitors | Variable trimmer 100pF | 1 |
| Ceramic 0.01µF | 1 | |
| Ceramic 0.1µF | 2 | |
| Electrolytic 33µF 25V | 1 | |
| Semiconductors | IC TA7642 | 1 |
| Transistor 2N3904 | 1 | |
| Inductor | Loopstick antenna with two inch ferrite rod with wound 26 gauge magnet wire around it and with 60-90 turns. | 1 |
| Speaker | 8Ω | 1 |
| Power Supply | 1.5V Battery | 1 |
The TA7642 chip is the heart of this AM radio receiver serving as both an AM RF amplifier and a detector.
It operates on a 1.5V battery and requires just a handful of passive components to work.
The antenna picks up signals, which are processed by an LC circuit made of L1 inductor and C1 helping to select the correct frequency range.
The TA7642 takes the incoming AM signal amplifies it and demodulates it to create audio signals.
Capacitor C3 connects the demodulated audio to a transistor amplifier stage made with transistor Q1, which is typically a regular NPN transistor.
The audio signal gets amplified once more before reaching a small speaker allowing you to hear the sound.
Formulas with Calculations:
Below are the formulas with calculations for Simple AM Radio Receiver Circuit using IC TA7642:
Tuned Circuit Resonant Frequency (LC circuit):
f = 1 / (2π√(LC))
where,
- f is the frequency in Hz
- L is the inductance in henry H
- C is the capacitance in farad F
Voltage Gain of Transistor Stage
Gain = Rc / Re
where:
- Rc is the collector resistor R4 is 100k
- Re is the emitter resistor R5 is 220Ω
Gain = 100000 / 220 = 454.5
This gain allows the weak audio signal from the IC to be amplified sufficiently to drive a small speaker.
How to Build:
To build a Simple AM Radio Receiver Circuit using IC TA7642 follow the below mentioned steps for connections:
- Gather all the components as mentioned in the above circuit diagram
- Connect GND pin 1 of IC1 TA7642 to GND of the circuit
- Connect INPUT pin 2 of IC1 to LC tank circuit of L1 inductor and C1 capacitor
- Connect the OUTPUT pin 3 of IC1 between resistor R2 and capacitor C3
- Connect collector of transistor Q1 to one end of 8 ohm speaker
- Connect the base of transistor to OUTPUT pin 3 of IC1 through capacitor C4
- Connect emitter of transistor Q1 to resistor R5 and capacitor C5 in parallel an GND
- Connect resistor R1 from the positive supply of 1.5V battery to the junction of resistor R2 and R3
- Connect the negative of 1.5V battery to GND
- Connect capacitor C2 one end from LC tank circuit of L1 inductor and C1 capacitor and other end of C2 capacitor connect to GND
- Connect a terminal of resistor R4 between capacitor C4 and base of transistor Q1 and other terminal connect to one end of o ohm speaker
Conclusion:
The Simple AM Radio Receiver Circuit using IC TA7642 is a small and simple project that is perfect for beginners and hobbyists.
It only needs a few parts making it a great way to learn about important ideas like radio frequency tuning, demodulation and audio amplification.
Because it uses very little power and is easy to assemble, it is great for teaching and for creating small portable radios.