The second-order multipurpose filter described here can perform as a low-pass, bandpass, high-pass, or notch filter at audio frequencies. What makes this filter unique is that all of its characteristics can be varied independently with potentiometers. In basic filters, only one k value is non-zero. Figure 1`s circuit includes the three basic types
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of filters. The characteristic frequency, Q value, and transfer gains are: When resistors R3, R4, and R8 have the same value, the parenthetical expressions are valid. R1 and R2 cause the characteristic frequency to change independently. To independently vary the Q value, R6 is adjusted. All of the gains change when R5 is modified. There are three useful outputs in the circuits. They are low-pass, high-pass, and bandpass outputs. In the circuit diagram, these are marked with abbreviations LP, HP, and BP. Replacing resistor R5 with the circuit in Figure 2 makes the gain adjustable. This method can also be used with the Q value. It`s possible to achieve adjustability by replacing resistor R6 with Figure 2`s circuit. The characteristic frequency adjustment is more complicated. To keep the adjustments independent, resistors R1 and R2 should be adjusted at the same time. This can be accomplished using the dual potentiometer as demonstrated in Figure 3. Although the pots are linear, the adjustment is logarithmic due to the virtual ground at the op amp`s negative input. The component values are selected so that the characteristics dependent on the potentiometer rotation follow Table 1. It must be emphasized that all the adjustments are independent. Gain adjustment has no effect on Q value or frequency. This is true for the Q value and characteristic frequency adjustments as well. There are several other types of filters that can...
This project fits more for custom made battery casing that can have more space to hide things inside. This switch with few alterations can be used for any other project as well but is designed based on e-bike needs! This project use a clever functionality of....
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In the past the sounding (sea bottom measurement) was done with the "bullet", that is, with a heavy lead object that the seamen plucked into the sea hung from a calibrated rope. As soon as the "bullet" reached the bottom, the depth appeared directly from the....
This Amplifier was designed to have the following specifications: Distortion less than 0.1% at full power of 100W even at 20KHz. Power has to be attributed to an extended bandwidth. The output transistors must be protected against short circuits. The power....
A series of LEDs serve to alert the gardener when plants need water. Using two conventional digital integrated LEDs and a series of LEDs, we make a very useful device for gardening. The device detects the amount of water in the pot and alerts the grower.....
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