TA7642 IC is very sensitive chip for AM radio.
It needs few extra parts and works on low voltage.
Circuit is good for small and efficient radios.
In this post we will see AM Radio Receiver Circuit using IC TA7642.
Here we have explained each part and have given easy steps to build.
TA7642 is new version of MK484 which is new version of old ZN414.
TA7642 and MK484 look like small transistor (TO-92 case).
Circuit Working:
Parts List:
| Component | Value/Type | Quantity |
|---|---|---|
| Resistors (All resistors are 1/4 watt unless specified) | 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 |
TA7642 is main part of AM radio which works as AM RF amp and detector.
Runs on 1.5V battery and needs only few passive parts.
Antenna gets signal and L1 coil and C1 capacitor chooses right frequency.
TA7642 amplifies and demodulates AM signal to audio.
C3 sends audio to Q1 transistor amplifier which is an NPN type.
Audio gets amplified again and then goes to small speaker to hear sound.
Formulas with Calculations:
Formulas for Simple AM Radio with TA7642:
Tuned LC frequency:
f = 1 / (2π√(LC))
where,
- f in Hz
- L in henry H
- C in farad F
Transistor stage gain:
Gain = Rc / Re
where,
- Rc is collector resistor for R4 is 100kΩ
- Re is the emitter resistor for R5 is 220Ω
Gain = 100000 / 220 = 454.5
This big gain makes weak audio strong.
How to Build:
To build a AM Radio Receiver Circuit using IC TA7642 follow the below steps for connections:
- Get all parts from circuit diagram.
- Connect pin 1 of TA7642 to GND.
- Connect pin 2 of TA7642 to LC tank L1 and C1.
- Connect pin 3 of TA7642 between R2 and C3.
- Connect collector of Q1 to one end of 8 Ω speaker.
- Connect base of Q1 to pin 3 of TA7642 through C4.
- Connect emitter of Q1 to R5 and C5 in parallel and then to GND.
- Connect R1 from +1.5 V to junction of R2 and R3.
- Connect negative terminal of battery to GND.
- Connect C2 from LC tank L1 and C1 to GND.
- Connect R4 between C4 and base of Q1 and connect other end to one end of 8 Ω speaker.
Conclusion:
This AM Radio Receiver Circuit using IC TA7642 is small and easy AM radio for beginners.
Few parts teach tuning, demodulation and amplification.
Circuit is with Low power, portable and good for learning.