Active Band Pass Filters

Active band pass filters are simply filters constructed by using operational amplifiers as active devices configured to simulate inductors. Active band pass filters are used largely at audio frequencies where otherwise the size of the inductor would become prohibitive. In this figure is multiple feedback band pass (MFBP) type which uses capacitors of equal value and leads us to simplified calculations.


Finally pick a convenient value for C which if reasonably large, leads to smaller values of resistance and consequently some aid in reducing noise. Valuable feedback (no pun intended) from readers using rate-this-page (see below and on every other page) indicates the following needs clarification. The 100 uF capacitor above is purely part of the power supply reservoir and has nothing to do with the filter itself. The two 10K resistors are part of the power supply biasing of the op amps because we are not using positive and negative power supplies. The capacitor and resistor values are simply the value of C you choose to use and the resistor values result from the following calculations. It's that simple.

50 Watt Amplifier Circuit Using Transistor

It is very rugged and reasonably power amplifier circuit that can be used for any audio applications. The amplifier produces 60W rms at 50V supply on a 8 Ohm load. The circuit is designed such that most of the components are not critical and can be easily replaced by nearest values. This make it ideal to assemble from your electronics junk box. This is a good design for room audio. This circuit is based on transistor for the operation. This is the figure of the circuit.


The capacitor C1 controls low frequencies and capacitor C2 controls high frequencies. The circuit is basically a class B amplifier. The transistors 2N 3055 serves the function of driving the speaker. The other transistor functions as pre amplifiers for the driver stage. This is the basic scheme of the circuit. The maximum power level of amplifier can be set by adjusting the 500 Ohm POT connected with the BC107 transistor. The circuit can be powered using a 50 V DC power supply with 5A current rating. Power supply up to 60 V can be given to the circuit. Any way the power supply must be well regulated and filters to avoid noise. Volume control can be attained by connecting a 10 K POT in series to the input of the amplifier, but in the figure is not shown. Adjust the 500 ohm POT to obtain optimum performance. All capacitors must be rated higher than the supply voltage.