Double-Sideband Suppressed-Carrier (DSB-SC) Modulator
When we modulate a carrier signal with amplitude modulation, there will be four frequency components as the result. The first is the modulating signal itself, the second is the frequency carrier, the the latest two are the difference and the sum of the carrier and the modulating signal. The spectrum of these frequencies can be …[Read More]
Voltage-Controlled Attenuator (Volume Control) Using FET
Using the circuit shown in the schematic diagram below, we can control the low-level audio signals with ±3V variable DC voltage. This attenuator circuit uses a field effect transistor (FET) to shunt the signal to ground. The R2 is used to control the output level (the attenuation level), but you can use other source of …[Read More]
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LM1201 Video Amplifier with Balanced (Bi-Phase) Output
This is a schematic diagram of video amplifier circuit with bi-phase output. Bi-phase output provides both positive-going and negative-going signal, and can be used as balanced signaling. The main component of this circuit is LM1201. In this circuit, the inverted video is obtained at pin 10 because of the 75Ω termination to the power supply …[Read More]
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]
Audible Logic Probe/Indicator
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]
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