If the motor was connected to the supply, then the collector of both BJTs could be connected to the second terminal, with all three sharing a common node. Adding a second transistor would allow for a total safe current draw of up to 2A–enough to power the motor. With multiple transistors in parallel, the current handling capacity can be better handled and prevents any individual transistor from sustaining damage.įor example, suppose we wanted to power a motor that required current (1.5A) larger than a single transistor (1A) could provide. Transistors in parallel can be used to help regulate current in the case that an individual transistor may not be sufficient. In the image, the nodes are electrically connected to the positive and negative terminals of the battery, and as such, all resistors have a voltage drop proportional to V. As shown in the image above, resistors R1, R2, and R3 all have an electrically common node at the bottom (which happens to be connected to the negative terminal of the battery), and an electrically common mode at the top (which happens to be connected to the positive terminal of the battery).Īs all components share two common electrical nodes, they all have the same voltage drop. In most circuits, wires are assumed to have zero voltage drop across them, and as such, all nodes that are connected by wires have the same voltage at that point. In a parallel circuit, all components have two common electrical nodes. Schematic showing R1 through R3 in parallel Another method of calculating the voltage drop across each resistor is treating it as a voltage divider and using the corresponding voltage divider equation. In order to calculate the voltage drop across each resistor, you can use Ohm’s law and multiply the current in the branch (the same current through each resistor) by its resistance. For example, the voltage source supplies a voltage and causes current to flow in the single branch in the circuit, through R4 all the way to R1. The term series circuit refers to the components connected end-to-end, as illustrated in the figure above. Schematic with resistors R1 through R4 in series ![]() parallel circuits with transistors, inductors, and capacitors. We’ll then be discussing more complex series vs. We’ll be providing basic examples with resistors as an arbitrary two-terminal device, but these definitions are also applicable to capacitors and inductors. Oftentimes, you will see subcircuits within a larger circuit that contain parallel elements or series elements. Of course, most circuits nowadays are neither purely series nor purely parallel, but a mix of both. Each component has the same voltage across it. In a parallel circuit, all components are connected, sharing two electrical nodes. All elements within the circuit have the same current running through them. In a series circuit, components are connected from end to end, creating a single path for current to flow. ![]() Ultimately, the difference between a series and parallel circuit can be summarized in the following two sentences. parallel resonant circuitsĪ figure illustrating a parallel circuit on the left and a series circuit on the right Parallel and series circuits utilizing transistorsĪ discussion of series vs. So, parallel circuits are really useful when you want your devices to keep working when one breaks or is removed.Learn the basics of elements in series and parallel It’s nought point nine amps here, and nought point three amps here, here and here.Īlso, because each of the routes has its own current running through it, if we remove one of the bulbs, the others stay lit. Placing ammeters at different points in the circuit shows how the current is shared between the branches. That’s because each branch has the same voltage across it, and only has the resistance of one bulb. In a parallel circuit, if you want to add more bulbs, you add them on their own branches of the circuit, like this. This simple circuit is like a one-bulb version of a building’s lighting circuit. ![]() Because, unlike a simple string of lights in a series circuit, these are all arranged in a parallel circuit.Īnd you can think of a parallel circuit as having several different routes that all run alongside, or parallel to, each other. In most buildings, the lights and sockets are all connected in big circuits but you can switch individual devices off, without affecting the others.
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