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Notch Filter: The Circuit’s Diagram and The Design Formula

circuit schematic

Notch filter is known as band-cut filter or band-reject filter. The fuction of this filter is to remove some frequency portion of a signal. The schematic diagram of this filter circuit, a second order notch filter is depicted in the figure below. The formula is actually complicated, but by taking the R3=R4 and [...]



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RS232 (COM) Port Pinout Diagram

circuit schematic

This pin diagram will be  useful when viewing these connectors. Sometimes you hold a soldering iron to the back of the connector, and you don’t remember the numbering of the pin. Here is the pin diagram for your reference: The number of each pins are actually  stamped on both sides of any D-type [...]



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DC-AC Inverter, Convert 12V DC Voltage to 110/220V AC Voltage

circuit schematic

The DC to AC inverter circuit shown in the schematic here is very simple circuit since it produce square wave, but it’s enough to power many devices. Here is the schematic diagram of the inverter circuit: The MOSFET is configured as bridge, so the current will flow alternatively in through the primary windings [...]



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Two Transistors Wireless Microphone (FM Transmitter)

circuit schematic

Please be warned if operating this circuit might violate the regulation of your country, because this FM transmitter circuit radiate strong radio frequency to the environment. This wireless microphone is very sensitive, pick up every sound in the 20m radius, and transmit the radio signal up to 2 kilometers in open air. Here is the [...]



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Fast Peak Detector

circuit schematic

Fast peak detector requires special amplifier features. The output stage must have high slew rate to keep up with the intermediate stages of the amplifier. This condition causes either a long overload or DC accuracy errors. The amplifier must deliver large currents into the capacitive load of the detector to maintain a high slew rate [...]



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Current Sense Circuit, A Classic Design Using Positive Rail Sensing

circuit schematic

A LT1637 is advertised as 1.1MHz, 0.4V/us Over-The-Top Micropower, Rail-To-Rail Input and Output Op Amp. This features are suitable for current sensing application since input voltages are right at the upper rail. The circuit show current sensing of 5V supply system, but  monitoring up to 44V application can be done by this circuit  (the maximum [...]



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