Basic Complementary (Push-Pull) Power Amplifier Circuit
This amplifier circuit is very popular audio power amplifier circuit type. We call it a complementary since the final transistors is an NPN-PNP pair, each with the same characteristics. This circuit produce an AB class amplifier, since each transistor works in slightly more than half cycle of the signal. There is overlap area when …[Read More]
Interfacing High Power Load to Logic Level with Optocoupler
Interfacing high power load can be done in many ways, such as using voltage divider resistors, transformer, or optocoupler. In the circuit shown below , an optocoupler method is presented. This optocoupler serve the logic level translation with flexible input, accepting wide range of voltage level, which is suitable for many high power load/devices. To …[Read More]
Logic indicator circuit / logic probe is used to identify logic level at any point of logic circuitry. The indicator can be visual (using LED, LCD, of 7 Segments) or auditory (using beeper or speaker). This circuit has a audible indicator, with the help of a loudspeaker to produce indication tone. Using the opamp,U1, as …[Read More]
Ni-Cad Battery Zapper, A Rechargeable Battery Reconditioner
Ni-Cad (NiCd, NiCad) battery, sometimes doesn’t work as expected, gives no power and cannot be recharged. In this situation, the battery need to be reconditioned. It’ is possible that the battery is internally shorted, and we can get the battery into life again by recondition the Ni-Cad battery using a zapper circuit. This circuit restore …[Read More]
Wien-Bridge Oscillator Using HA2541 Op-Amp
A Wien-Bridge oscillator circuit can be built from HA2541 and some basic components. This circuit can generate good-quality sine wave of 40 MHz with an upper limit of 50 MHz. The R3 through R7 and D2 and D1 provide the diode limiting for this circuit. Here is the schematic diagram of this circuit: For frequency …[Read More]
Automotive/Car Power Adapter For 3V, 6V, or 9V DC Operated Devices
In automotive environment, it’s common that only single voltage power outlet is available. Using the very popular LM317 voltage regulator IC, we can build a general purpose DC adapter to adapt car’s power outlet voltage (12-14 Volts) to supply small DC devices requiring lower voltage level. On the following schematic diagram for the car power …[Read More]
Three Wire RS232 To RS485 Converter
The schematic diagram below show the circuit diagram of an RS232 to RS485 converter circuit. The EIA-485 standard, a.k.a TIA/EIA-485 or RS-485, is a physical layer standard defining the electrical properties of electronic drivers and receivers using balanced digital signal which is capable of handling multipoint systems. The ANSI Telecommunications Industry Association/Electronic Industries Alliance …
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