Triangle And Square Waveform Generator

V2 output is TTL compatible
R2 adjusts to symmetry of the triangle waveform
Frequency is adjusted with R5 and C

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Microphone Amplifier

This circuit operates from a 1.5 Vdc source.

Low-Impedance Microphone Preamp

This amplifier uses a common-gate FET amplifier to match a low-Z microphone.

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General-Purpose Preamp

This amplifier is useful for audio and video applications. Gain is set by Rf and the voltage gain of this amplifier is approximately 1+Rf/560, where Rf is in ohms. Bandwidth depends on gain selected, but typically it is several MHz. Rf=5.1 kW, which produces a gain of 10*(20dB) voltage.

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Audio Volume Limiter

IC1-a is connected as an inverting amplifier whose gain is controlled by the LDR portion of an optocoupler.

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