Portable Calibrator: Stable 10V Reference

A stable voltage source is needed in many calibration process. Most electronic devices are affected by its surrounding temperature. To control all the components temperature by manipulating the surrounding temperature is not easy, but fortunately we can control only the most critical component to produce a stable voltage. The most critical component in a voltage reference is the reference diode, […]

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Long Interval RC Timer Using Op-Amp

With the help of high gain high impedance operational amplifier, we can build a long time delay with resistor-capacitor (RC) circuit since it allow high resistance resistors to be used. We can calculate the time (t) using the following formula; Time (t) = R4.C.ln(Vr/(Vr-Vi)). For design example is a 100 second timer, where this circuit uses this following components: Vr=10V, […]

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Speech-Pass Filter

A speech-pass filter circuitry is shown in the the schematic diagram below. This speech circuit is useful in an application when the frequency spectrum of the signal should be limited to contain only speech (human voice) information. Voice recording or radio broadcasting is some example of such application. Corner frequencies of 300 and 3000 Hz is provided by high pass […]

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