Free electronic circuit design and schematic diagram
This is a Twin-T Notch Filter circuit. This circuit is a filter that can remove a certain frequency band. This is a passive filter that uses two filters in parallel, high-pass and low-pass. The high-pass filter is lower one and the low-pass filter is the upper one. This filter has a problem with the input resistance. When this filter is […]
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This bass booster circuit can be used filter the input signal as part of internal circuit of an active subwoofer circuit. This circuit is not only boost the bass (low) frequency, but also attenuate high frequency as well. You might consider this circuit as low pass filter, since the high frequency response is not flat, not really as expected in […]
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As shown in a schematic diagram below, this circuit implementation of phase shifter circuit is well suited to using digital potentiometer to control the resistive control element of the phase shifter. The phase at a given frequency is now under control of a digital signal using this circuit which is optimized for phase-shifting over the audio range. By using a […]
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We can use tone/frequency detector (decoder) to detect the presence of a signal with a certain tone. The output of the circuit will be active if the signal is the same tone with the tone of a series of internal oscillator. LM567 is one of decoder that we can use. The LM567 and LM567C are general purpose tone decoders. Both […]
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Gyrators are synthetic inductors, which are often used to form bandpass filters. As shown in the two examples here, the active buffering device can be a transistor or op-amp. This type of bandpass filter is commonly used in graphic equalizers and other frequency control circuits such as tone controls. In the gyrator frequency calculator here, enter the values of R1, […]
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The R1/C1 network makes a low pass filter when the wiper is at the grounded end of the tone pot, and there is a treble cut. The C1 cap bypasses R2 when the wiper is adjusted so that it is at the top end of the pot and it creates a treble boost. The 100k output volume and the 100k […]
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Variation of the famous Baxandall circuit is shown in the passive circuit in figure 1. Smoothly increasing +- 6 dB/octave slope of boost or cut is the feature of this circuit. Although the “shelves” are outside the audible range with these component values, the bass and treble filters have a shelving response. The threshold and shelving frequencies is predicted by […]
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