Author Archives: Rend

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MAX1703 Single-Cell Boost Converter Circuit

When you design a circuit with only a single-cell battery, you will need boost-converter to provide enough voltage for most ...

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55MHz Scope Sensitivity Amplifier

Scope sensitivity amplifier is a vital front-end signal processing for every scope instruments. The function of this circuitry is simple: ...

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Two-Band Bxandall Active Tone Control

Using active circuit for tone control means that we can provide cut and boost, maintaining overall amplifying factor of original ...

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Pulse Width (PWM) Controller Circuit

A LM3900 quad operational amplifier can be used to build a pulse width (PWM) controller. The LM3900 was chosen because ...

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Small TV Modulator Using A Motorola MC1374

How can television modulator be small and simple like this? First, it uses integrated circuit, and the second, any TV ...

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Low Cost Precision Light Control / Dimmer

Using a the controlled-half-plus-fixed-half-wave phase control method, this circuit can regulate an 860 a watt lamp load from half to full power. This circuit control the light output of the lamp from 30% to 100% because Half power applied to … Continue reading

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Phone Incoming Call Flasher

This is a circuit of phone message flasher, an alternative way to get alarmed when there is an incoming call. When the phone rings, high line voltage will be detected by A differential amplifier with hysteresis (Q2, Q3, and Q1). … Continue reading

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Burglar Alarm Works for Both N.O and N.C Contacts

Unlike other alarm circuit that provide normally-open only or normally-closed only configuration, this alarm circuit work for both configurations. The mechanism of this alarm circuit is very simple, that the output will be active (Q1 transistor will be conducting) if … Continue reading

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Electronic Gain Control in Quartz-Stabilized Oscillator

This is a quartz-stabilized oscillator circuit with electronic gain control. Replacing the common filament lamp  for amplitude stabilization, this circuit use an electronic gain control inside the stabilization loop. A 50-Ω variable resistor should be trimmed until the output level … Continue reading

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