### Parallel Circuits

We mentioned prior, that there were 2 types of circuits, SERIES and PARALLEL. So far, all we have talked about is series. Now we are going to discuss the difference between a series and a PARALLEL circuit. In the series circuit, all the electricity followed the same path. In our waterflow representation, this meant that all the water flowed through 1 pipe. In PARALLEL circuit, however, there are multiple paths that current can flow through.

Notice that in the picture to the left, that there are 3 different paths which the water can take. All 3 paths have the same incoming pressure, but the flow of some paths can be more restricted than in others. Parallel circuits in electronics work on the same principle. While there may be multiple paths for the electricity to flow through, the electrical pressure (Voltage) remains the same through all paths.

As you can see from the diagram on the right, there are 4 meters placed in this circuit to measure the current. The first 3, (A 1 , A 2 , and A 3 ) measure only the current flowing through that individual leg of the circuit. The 4th, A T measures the Total current of the circuit.

If you take the three individual currents, and add them all together, they will equal the total current, measured on the 4th meter. From this we can see that the current in a parallel circuit is additive.

Resistance in a parallel circuit can be quite a bit trickier than in a series circuit. It is found by " Reciprocating the Sum of the Reciprocals ". (huh?)Simple. Taking the reciprocal of a number means dividing "1" by that number. The reciprocal of 2 would be 1 divided by 2 or ½. Most modern calculators have a [1/X] button just for this purpose. So if you take the reciprocals of the values of all of the resistors, which would, of course, give you a bunch of fractions, and add them all up, then reciprocate their sum, you would have the answer. The formula would look something like this:

Confused yet? Good.... let's see if we can clear it all up in lesson 13!

# Parallel Circuits - the Plague!

Now that I have you thoroughly confused, let me make things as clear as mud for you. Let's begin with a very simple circuit: 2 resistors and 1 battery. You are given the following information about the circuit:

A 1 reads .2 Amps in current ( I=.2 )

Find:
Total Voltage
Total Circuit Resistance
Total Current
And Finally, the Current through A 2

Now this isn't as tuff as it first looks. Let's break the problem down. We know according to Ohm's law, that if we know the resistance and current, we can find the voltage.
E R1 = I R1 x R 1 .
E = .2 x 50 = 10
E = 10 Volts.

Now that we know that the voltage for the entire circuit is 10 volts, let's find the total Resistance.
First, we find the reciprocals of the individual resistances:
R 1 = 50 ohms. 1/50 = .02
R 2 = 200 ohms. 1/200 = .005
Now we add the two reciprocals together:
.02 + .005 = .025

Finally we take the reciprocal of the sum:
1 / .025 = 40 Î©

So if the Total Voltage of the circuit is 10 Volts, and the Total Resistance = 40 Î© then by using Ohms Law again we can find the total current.
I Total = E Total / R Total
I = 10/40 = ¼ Ampere.

Almost finished now. So far we know:
A 1 reads .2 Amps in current ( I=.2 )
V Total = 10
R Total = 40
and
I Total = ¼

Now we have at least 2 methods by which we can find the current through A 2 .
We know that the Total current is the sum of all the individual leg currents, so if we subtract the current of A 1 from the Total current we get this:
I Total - I 1 = I 2 .25 - .2 = I 2 = .05 Amperes.

The other method would be by using Ohms Law. We know the resistance of R 2 = 200 Î©. We also know that the voltage across R 2 = 10 Volts. Hence:
10 Volts / 200 Î© = .05 Amperes.

Either way, our final result is A 2 = .05 Amps

# Series and Parallel Resistances - a Summary

To summarize all that we have just learned:

• There are 2 types of circuits.... Series and Parallel.
• Series Circuits
• Are connected in a straight line, like a chain.
• All current remains the same throughout the circuit.
• I Total = I 1 =I 2 =I 3 etc...
• There can be many different voltages in a series circuit, as a voltage drop appears across every resistor.
• The total voltage in a series circuit is equal to the sum of all the individual voltage drops within the circuit.
• E Total = E 1 + E 2 + E 3 + etc...
• The total resistance in a series circuit is equal to the sum of all the individual resistances within the circuit.
• The formula for Resistance in Series is:
R Total = R 1 + R 2 + R 3 + etc...
• Parallel Circuits
• Are connected allowing multiple paths for current flow.
• All voltage remains the same throughout the circuit.
• E Total = E 1 =E 2 =E 3 etc...
• There can be many different currents in a parallel circuit, as each leg has the same voltage, but can have a different resistance.
• The total current in a parallel circuit is equal to the sum of all the individual currents on each leg of the circuit.
• The formula for Current in Parallel is:
I RTotal = I R1 + I R2 + I R3 + etc...
• Resistance is found by reciprocating the sum of the reciprocals of the resistance of the individual branches
• The formula for Resistance in Parallel is:
1
-----------------------------------
1       1       1       1       1
---- + ---- + ---- + ---- + ---- +
R 1     R 2    R 3    R 4    R X...
• Ohm's Law states that there is a relationship which exists between current, resistance, and voltage, such that E = I x R

### 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 …