In electronics, a voltage divider is a simple device designed to create a voltage (V_out) which is proportional to another voltage (V_in). It is commonly used to create a reference voltage, and may also used as a signal attenuator at low frequencies. Voltage dividers are also known by the terms resistor divider and potential divider. Electronics is the study of the flow of charge through various materials and devices such as, semiconductors, resistors, inductors, capacitors, nano-structures, and vacuum tubes. ... International safety symbol Caution, risk of electric shock (ISO 3864), colloquially known as high voltage symbol. ...

Resistor divider

A voltage divider referenced to ground is created by connecting two resistors as shown in the following diagram: It has been suggested that Ground conductor be merged into this article or section. ...

Image File history File links No higher resolution available. ...

The output voltage V_out is related to V_in as follows:

It may be useful to note that R₁ and R₂ may each comprise many resistors in series.

As a simple example, if R₁ = R₂ then

As a more specific and/or practical example, if V_out=6V and V_in=9V (both commonly used voltages), then:

and by solving using algebra, R₂ must be twice the value of R₁. Algebra is a branch of mathematics concerning the study of structure, relation and quantity. ...

Any ratio between 0 and 1 is possible. That is, using resistors alone it is not possible to either reverse the voltage or increase V_out above V_in

Voltage divider as a voltage source

While voltage dividers may be used to produce very precise reference voltages, they make very poor voltage sources. This is because if a load is connected between the output voltage and ground the effective resistance between V_out and ground decreases. A change in the resistance of R₂ changes the load voltage, an undesirable situation for a voltage source. This article or section does not adequately cite its references or sources. ...

In terms of the above equation, if current flows into a load resistance (through V_out), that load resistance must be considered in parallel with R₂ to determine the voltage at V_out. In this case, the voltage at V_out is calculated as follows: This article or section does not adequately cite its references or sources. ...

where R_L is a load resistor in parallel with R₂.

Note that for high impedance loads it is possible to use a voltage divider as a voltage source, as long as R₁ and R₂ have very small values compared to the load. This technique is rarely used, as the power disipated in such a divider would be considerable. In digital circuits, high impedance a voltage that is lower than the threshhold for a digital 0. ...

Use of voltage dividers

Voltage dividers are often used to produce stable reference voltages. These reference voltages may be used at a device with a high input impedance, such as an op-amp without fear of loading the divider. Alternatively, the reference voltage may be used to set the voltage being produced by a voltage source. A simple way of doing this (for low power applications) is to simply input the reference voltage into the non-inverting input of an op-amp buffer. An operational amplifier or op-amp is an electronic circuit module (normally built as an integrated circuit, but occasionally with discrete transistors or vacuum tubes) which has a non-inverting input (+), an inverting input (-) and one output. ... It has been suggested that this article or section be merged with Current source. ... A buffer amplifier (sometimes simply called a buffer) is one that provides impedance transformation from high to low between one circuit and another. ...

A voltage divider is commonly used to set the DC bias of a common emitter amplifier. R1, R2 and RE provide bias in this common emitter amplifier (CEVDB) circuit configuration Biasing in electronics is the method of applying a predetermined voltage and current to the junction of a transistor to set the appropriate quiescent point. ... Common emitter amplifier, voltage divider bias (CEVDB) circuit configuration A common emitter is a type of electronic amplifier stage based on a bipolar transistor in series with a load element such as a resistor. ...

Impedance divider

A voltage divider is usually thought of as two resistors, but for electronics signals at a given frequency capacitors, inductors, or any combined impedance can be used. For general impedances Z₁ and Z₂, the voltage becomes Capacitors: SMD ceramic at top left; SMD tantalum at bottom left; through-hole tantalum at top right; through-hole electrolytic at bottom right. ... An inductor is a passive electrical device employed in electrical circuits for its property of inductance. ... Electrical impedance, or simply impedance, is a measure of opposition to a sinusoidal alternating electric current. ...

For instance, a divider can be made with a resistor and capacitor:

Image File history File links Capdivider. ...

The resistor's impedance is simply its resistance:

Z_R = R

The capacitor's impedance is a large resistance at low frequencies and a low resistance at high frequencies. The exact formula is: Sine waves of various frequencies; the lower waves have higher frequencies than those above. ...

where C is the capacitance of the capacitor, j is the imaginary unit, and ω is the frequency of the input voltage which is measured in radians per second. This divider will then have the voltage ratio: Capacitance is a measure of the amount of electric charge stored (or separated) for a given electric potential. ... In mathematics, the imaginary unit (or sometimes the Latin or the Greek iota, see below) allows the real number system to be extended to the complex number system . ... FreQuency is a music video game developed by Harmonix and published by SCEI. It was released in November 2001. ... Some common angles, measured in radians. ...

The ratio then depends on frequency, in this case decreasing as frequency increases. This circuit is, in fact, a basic (first-order) lowpass filter, or, in the world of audio, a treble-cut filter. The ratio contains an imaginary number, and actually contains both the amplitude and phase shift information of the filter. To extract just the amplitude ratio, calculate the magnitude of the ratio, or just use the reactance of the capacitor instead of the impedance. A low-pass filter passes low frequencies fairly well, but attenuates high frequencies. ... Waves with the same phase Waves with different phases The phase of a wave relates the position of a feature, typically a peak or a trough of the waveform, to that same feature in another part of the waveform (or, which amounts to the same, on a second waveform). ... The magnitude of a mathematical object is its size: a property by which it can be larger or smaller than other objects of the same kind; in technical terms, an ordering of the class of objects to which it belongs. ... It has been suggested that Electric reactance be merged into this article or section. ...

See also

• Potentiometer
  • especially Theory of operation
• Wheatstone bridge
• Current divider

The present popular usage of the term potentiometer (or pot for short) describes an electrical device which has a user-adjustable resistance. ... The present popular usage of the term potentiometer (or pot for short) describes an electrical device which has a user-adjustable resistance. ... A Wheatstone bridge is a measuring instrument invented by Samuel Hunter Christie in 1833 and improved and popularized by Sir Charles Wheatstone in 1843. ... The Current Divider (or division) rule (Sometimes referred to a CDR) is used to find the current flowing through an impedance or other circuit when it is connected in parallel with another impedance. ...

External links

• Calculator: voltage divider - loaded and open circuit
• Lesson In Voltage divider

References

• Paul Horowitz and Winfield Hill, The Art of Electronics, Cambridge University Press, 1989.