### Resonance

In this circuit, we have a resistor, a capacitor, and a coil in series. Because the coil and the capacitor act in an opposite manner, they tend to cancel each other out. We say that the coil is additive, and the cap is subtractive in nature. If the inductive reactance, and the capacitive reactance were equal in value, they would effectively cancel each other completely out, and only the resistance would be seen. In this special case, we would say that we have a resonant circuit (we'll explain the term in more detail in a little bit).

Just as we must solve problems with resistance in series... we must also be able to add the various reactances together, and come up with a common ground. Resistance is pure resistance. Capacitive reactance is a resistance that is subtractive in nature. Inductive reactance is additive in nature. Combining the three, we come up with a new term called IMPEDANCE, which is symbolized by the letter Z. Just like resistance, the formula is different for impedance in series and in parallel. The formula for impedance in series is:
If we plug in the values in the example above, we can solve the formula like so:

Note that this method is not much different than what we did in lesson 25. There we added phase "vectorally". This is a function of trigenometry, where in a given triangle, A2+B2=C2. (The square of the hypotenuse is equal to the sum of the square of the two sides). The same applies here.

We can say that the A2 is the resistance, the B2 is the combined capacitive and inductive reactances, and the C2 is the Impedance ( Z ).

We could plot out our capacitance and inductance vectorally, but this would use up lots of time and paper. We can simply solve the same problem using this formula, where the B2 is equal to the sum of the reactances of the coil and the cap. We always subtract the capacitive reactance from the inductive reactance, because capacitors are subtractive.

So if I hate math so much, why do I say that this is where the real fun begins? You'll see!

Let us assume a circuit with both a resistor, a capacitor and an inductor. We will use small numbers here for simplicity.

If the value of the resistor is 4 ohms, the value of the inductor is 3 ohms, and the value of the capacitor is -3 ohms. (Remember that capacitors are negative in nature). The 3 ohms of capacitive reactance (X C )will negate the 3 ohms of inductive reactance (X L ), and the overall resistance is figured as follows:

R Total = R + X L - X C
R Total =  4 + ( 3    -    3  )

Whenever a circuit has both inductors and capacitors, there is a given frequency at which X L is mathematically equal, but opposite to X C . In this case, X L is +3 and X C is - 3.

When this happens, the Total Resistance is equal to the pure resistance of the resistor, and the capacitor and inductor cancel each other out for all intents and purposes. We say then, that the circuit is in RESONANCE .

When a circuit is resonant, it is at its lowest point in resistance. Any increase, or decrease in frequency will cause the circuit to have greater resistance.

But because a circuit has less resistance at it resonant frequency, it will allow more of a signal to pass through at resonance than at a higher or lower frequancy than the resonant frequency.

The frequency at which the circuit becomes resonant is (for our purposes) completely dependant on the inductance and capacitance of the circuit. The "pure" resistance of the circuit does not affect the resonant frequency of the circuit.

Circuits which are resonant at a given frequency are said to be TUNED to that frequency. These are sometimes called TUNED CIRCUITS .

They may also be called FILTERS , because they are used to "filter" one set of frequencies apart from all the others within a given band of frequencies. In some circles, tuned or resonant circuits are referred to as TANK CIRCUITS , although I'm not exactly certain why. It has always been my belief that this referred to Tuned Cavities in waveguide, which resemble a tin can or tank in nature. But I have yet to substantiate this idea. Just keep in mind that if you hear someone refer to a tank circuit, they are talking about a tuned filter.

### Build a Low Noise And Drift Composite Amp Circuit Diagram

How to Build a Low Noise And Drift Composite Amp Circuit Diagram. This circuit offers the best of both worlds. It can be combined with a low input offset voltage and drift without degrading the overall system`s dynamic performance.
Low Noise And Drift Composite Amp Circuit Diagram

Compared to a standalone FET input operational amplifier, the composite amplifier circuit exhibits a 20-fold improvement in voltage offset and drift. In this circuit arrangement, A1 is a highspeed FET input op amp with a closed-loop gain of 100 (the source impedance was arbitrarily chosen to be 100 kfl). A2 is a Super Beta bipolar input op amp. It has good dc characteristics, biFET-level input bias current, and low noise. A2 monitors the voltage at the input of A1 and injects current to Al`s null pins. This forces A1 to have the input properties of a bipolar amplifier while maintaining its bandwidth and low-input-bias-current noise.

### High Power Output Amplifier TDA7294

The famous SGS-THOMSON ST Microelectronics has introduced a Hi-Fi DMOS high-power amplifier circuit TDA7294, its sound great taste bile, which due to its internal circuit from input to output are field-effect devices, rounded sound Mild, delicate Rounuan.  However, with its assembly amplifier, only TDA7294 single-output power is only 70 W, BTL access law is 100 W from top to bottom, do not feel that power cushion. The author several tests, used to promote TDA7294-level, direct-drive one to four pairs of high-power transistor parallel, the output of strong currents, the power output of 400 W (mono), and the circuit is simple and no need to debug that can reliably work Basically, the IC has maintained a sound and performance.  Ruzuo The figure below shows, R6 for the feedback resistor, the author of the value in debugging 22 k Î© more appropriate, R6 also decided this circuit gain, the gain value will increase.  Quiescent current depends on the power of R7, R8, when its value…

### Full Power Mobile Phone Jammer Circuit Diagram

Full Power Mobile Phone Jammer Circuit Diagram.To day if we are talking about expert Cell phone Jammers we are conversing about this schematic underneath. First off all you should be very very cautious how to use this apparatus. Its completely illegal and so the reason. I post this Circuit is only for educational and testing causes. This type of apparatus is being utilised by security for VIPS, particularly at their limousines to avoid blasting device initiating while the vehicle passes from the goal cell phone-bomb. Off course there are those who use it to make a antic or to make the persons crazy in the rectangle block you are.
The power of the jammer is currently sufficient to do your thing, but certainly you can place a 30W linear power amp at the RF output and impede a much wider locality. So, Be pleasant individual with that and recall that there are people who may need desperately to obtain or make a call and one of them could be you! And if you can't oppose of functioning …