Posted on Saturday, March 31, 2012 • Category: Amplifiers
A general purpose audio power amplifier is a must have for the electronics amateur. It's not a good thing to use your HiFi set for an experiment, when there's a risk of blowing it's transistor out. Amplifier for your experiments should be simple in construction, durable, and easy to repair. Also a portable, low power consumption and battery powered.
Taking the considerations above, I gave you the PCB design for the TBA820M based amplifier. It is rated for 2Watts of RMS power output (16W PMPO) but gives even two times more if you cool it well by some tricks. I've been using this circuit for over ten years and personally still surprised by it's durability, thinking of how many short circuits and overdrives it is subjected.
Posted on Friday, March 23, 2012 • Category: Test and Measurement
Presented here is zener diode meter for testing voltage value of an unknown zener diode. The zener diode or diode voltage regulator is a special diode, Unlike normal diodes these diodes are intended to work in the breakdown voltage and an essential part of the voltage regulator circuits.
These components maintain constant voltage at its terminals suffer variations even when substantial current, its connection with reverse bias is normal also to work in the zener voltage of the source Vs must be greater than the rupture Vz, as always condition using a resistance Rs in series to limit current to a value always less than its maximum power.
Posted on Tuesday, March 20, 2012 • Category: FM Transmitters
The RF oscillator using the inverter N2 and 10.7Mhz ceramic filter is driving the parallel combination of N4 to N6 through N3.Since these inverters are in parallel the output impedance will be low so that it can directly drive an aerial of 1/4th wavelength. Since the output of N4-N6 is square wave there will be a lot of harmonics in it. The 9th harmonics of 10.7Mhz (96.3Mhz) will hence be at the center of the FM band. N1 is working as an audio amplifier. The audio signals from the microphone are amplified and fed to the varicap diode. The signal varies the capacitance of the varicap and hence varies the oscillator frequency which produce Frequency Modulation.
Posted on Monday, February 20, 2012 • Category: Power Supplies
Split power supply provides a stable regulated bipolar voltage in the range ±1.5V to ±17V. It is based on LM317/LM337 linear voltage regulators that also have a short circuit protection. Most parts are easily accessible, including a 6"x3"x2" project box, 12V 1.2A center tap transformer, pots, knobs, etc. Power supply schematic shows how to wire LM317/LM337 to get +/- split voltage output.
Posted on Wednesday, February 15, 2012 • Category: FM Transmitters
With this circuit you can build a very small tracking transmitter that can be tracked using a FM broadcast band radio receiver. The transmitter can be powered from any 1.5V volt battery or power supply. Transmitter has a range up to 1 mile depending on battery voltage, height above ground, receiver sensitivity, and antenna length. Under certain conditions distances of 1 mile have been achieved. It is recommended that this transmitter be used with FM radios that can tune continuously across the dial. The better the receiver and receiver antenna system the greater the practical range of the transmitter, however good functionality can be achieved with the least expensive radios and using only the standard telescoping antenna included with most radios.
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