Why so many resistors?

Question

Hello.


When I look at circuit diagrams, they often seem to have lots of unecessary reistors.

They are in series with other components, or in series. I often wonder why they are there.

Thanks.

Answer 1

Normally resistors are used to limiting current into certain critical components, or in comparator or amplifier circuits, and in tuned circuits with capacitors and/or inductors.

Certain resistor values may not be available and so two may be needed in series.

In mass produced circuits, designers may use resistors in series in order to make a value that is not available as a single resistor. Economics may dictate that it is cheaper to use two resistors that are used in massive quantities than a small number of specialist resistors. This could be due to large batch quantities being cheaper, or loading pick and place machines less times being more efficient. Often production engineers will take a circuit design and look at ways of manufacturing it cheaper by such means.

Answer 2

Consider the flow of electric current to be similar to the flow of water. Resistors are like pipe valves to control the flow of electric current. Many resistors have fixed values but others (potentiometers or pots) can vary current (like opening and closing a valve). Your house likely has many valves including some left shut, open or throttled when needed to serve the many purposes of the piping system. Same goes for complex electrical circuits that must be 'tuned' of limit current (or reduce electrical pressure?) to avoid component damage. Great question.

Answer 3

Designers do not put components in for nothing. These resistors can perform many different things dependant on the circuit configuration. These range from limiting current, providing certain voltages for biasing semiconductors, changing time constants, frequency response, etc in conjunction with other components.

If you learn enough about electronics it will all become clear.

Answer 4

Resisters serve as voltage regulation, and some components need less voltage than others. Resistors that are in series together are that way only when it would be more expensive to put the resistor of proper value into the circuit.

Answer 5

Resistors are used to restrict current flow. But another common usage is to create voltage dividers by placing two or more in series. This allows for the creating of diffeent voltage levels from one common power source.

Thes voltages are typically used to bias amplifiers and to serve as thresholds in comparator circuits.

Answer 6

Resisters are use to limit the amount of voltage/current passing through that path to a certain component.

Answer 7

basicaaly they are there to step down the voltage to the component or components in the circuit, as not all components can handle the full input voltage