Category Archives: Signal Processing

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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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Opto-Coupled Discrete Pulse Stretcher

This is a pulse stretcher circuit using optocoupler. This circuit uses a 4N26 opto-coupler combined with a standard one-shot circuitry. This circuit is triggered by pulse about 3μs (minimum width)  at 15mA. The output’s amplitude of this circuit is not … Continue reading

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Bandpass Filter for Bell103A Originator Modem

Bell103A modem standard specify that the originator (the caller) uses 1070Hz and 1270Hz frequency shift keying for transmission, and listen for 2025/2225Hz FSK transmitted by the answering modem. This bandpass circuit filter out any frequency beyond 2025-2250 Hz to improve … Continue reading

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Five-Decade Dynamic Light-Level Meter

This is a Portable light-level meter circuit with five-decade dynamic range. This uses  a single cell battery as the power supply. To calibrate this circuit, use an appropriate illumination, then adjust R2 so that the output equals the reference. To … Continue reading

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Single Transistor Variable 0-180 Deg Phase Shifter

The schematic diagram below shows a variable 0-180 degree phase shifter circuit. This circuit can provide  phase shifted output (compared with the input) between 0 and 180 degrees for frequencies up to 3MHz with same amplitude (unity gain or gain=1.) … Continue reading

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