Long Period SCR Timer

This is a SCR timer circuit. Here, SCR is used to drive the final actuator, the buzzer.  The time constanst of this circuit is determined by  R1 and C1. The buzzer will sound when C1 charges up to a desired level, it will cause the Q1 to conduct and triggers SCR1.  The use of FET for Q1 make the RC […]

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20 kHz Astable Multivibrator with Transistors

Astable multivibrator or oscillator circuit is based on positive feedback. We can design such circuit using op-amp, logic gates, or transistors. Here we can rely on single capacitor capacitor and resistor for the feedback inside op-amp like transistor circuit, which works over wide range of temperature, voltages and transistor gains. The stability is pretty good, for supply voltage changes between […]

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Logarithmic Amplifier Using MC1556 Op-Amp

The circuit below is a logarithmic amplifier using an MC1556 op amp. The 10K pot is an offset adjustment.  Here is  a schematic diagram of one classic example of  general purpose  logarithmic converter circuit employing LM1556 op-amp: The popularity of logarithmic amplifier is decreasing as the microprocessor and microcontroller chips are  getting lower and lower in price. Long time ago, […]

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TC9400 Wide Frequency Range Pulse Generator

The reason why TC9400 V/F converter is very useful in the laboratory are because it’s portable, battery-operated, and low cost frequency source. Both pulse and square-wave outputs are provided by the TC9400. A triangular waveform can also be generated by adding an op-amp integrator. The outputs can be frequency-modulated via the FM input. [Circuit’s schematic diagram source: Microchip Application Note]

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