Voltage Divider Symbol
Definition: The Voltage Divider symbol represents two resistors connected in series between an input voltage (Vin) and ground, with the output voltage (Vout) tapped at the midpoint junction between the two resistors, producing an output that is a fixed fraction of the input voltage as defined by the resistor ratio R2/(R1 + R2), a fundamental circuit topology standardised under IEC 60617 and ANSI Y32.2 / IEEE 315 using standard resistor symbols.
Also known as: potential divider, resistor divider, resistive attenuator, voltage scaler, voltage splitter.
What the Voltage Divider symbol means
The Voltage Divider symbol denotes the most fundamental passive voltage-scaling circuit in electronics: two resistors (R1 and R2) in series, with the input voltage applied across both and the output taken from the node between them. The output voltage Vout equals Vin multiplied by R2/(R1 + R2). When R1 equals R2, Vout is exactly half of Vin. This relationship is exact only when the load connected to Vout has an impedance much greater than R2; any load current through R2 modifies the effective R2 value and reduces Vout below the ideal value.
In schematics, the Voltage Divider symbol communicates a deliberate signal-scaling decision. The symbol typically shows two resistors drawn vertically in series, with Vin at the top, GND at the bottom, and Vout emerging from the midpoint node as a horizontal tap. The designators R1 and R2 (or the specific resistor values) are labelled next to each element. Understanding this topology is essential for reading analogue circuit diagrams, as voltage dividers appear in biasing networks, ADC input conditioning, pull-up and pull-down networks, and Wheatstone bridge circuits.
How to identify the Voltage Divider symbol
The Voltage Divider symbol is drawn as two resistor symbols (rectangles in IEC, zigzags in ANSI) stacked vertically in series, with a wire at the top connecting to Vin and a wire at the bottom connecting to GND. A horizontal branch exits the node between the two resistors to form the Vout terminal, often indicated by a dot (junction marker) at the midpoint. The upper resistor is designated R1 (series element) and the lower resistor R2 (shunt element). The overall shape resembles the letter T rotated 90 degrees, or an upside-down Y.
Function in a circuit
In a circuit, the Voltage Divider functions as a passive, lossless-free voltage-scaling network that produces a lower output voltage proportional to the input. R1 drops voltage from Vin to the midpoint; R2 drops the remaining voltage from the midpoint to GND. The output voltage at the tap is Vout = Vin x R2/(R1 + R2). Because both resistors carry the same series current (Vin/(R1+R2)), any load connected to Vout must have an impedance at least 10-100 times R2 to avoid loading error. The voltage divider is a linear, frequency-independent (at low frequencies) passive attenuator with no gain greater than unity.
Standards: IEC vs ANSI
| IEC 60617 | IEC 60617-04 defines the individual resistor symbols (filled rectangle) used in the voltage divider topology. IEC 60617 does not define a combined voltage-divider composite symbol; the circuit is drawn using individual IEC resistor symbols in series with a tapped midpoint connection. |
|---|---|
| ANSI/IEEE 315 | ANSI Y32.2-1975 / IEEE 315-1975 defines the zigzag resistor symbol used in the ANSI voltage divider circuit. As with IEC, no combined voltage-divider composite symbol is standardised; the topology is drawn using two ANSI resistor symbols in series. |
| Key difference | The IEC voltage divider uses two filled-rectangle resistor symbols in series; the ANSI version uses two zigzag resistor symbols. The circuit topology, node labelling (Vin, Vout, GND), and function are identical between both standards. |
Terminals / pins
| Pin | Name |
|---|---|
| vin | Vin |
| vout | Vout |
Typical values
Output voltage: Vout = Vin x R2/(R1 + R2). Resistor values: any values from ohms to megaohms; typical bias dividers use 10 kOhm to 100 kOhm to balance power consumption and loading error. Voltage accuracy: limited by resistor tolerance (typical 1% or 0.1%). Maximum power dissipated: Vin^2/(R1+R2) watts (must stay within resistor power ratings).
Where the Voltage Divider symbol is used
- Biasing transistor base or gate terminals to set the operating point (Q-point) in amplifier circuits
- Scaling analogue sensor voltages (0-12 V or 0-24 V) to the ADC input range of a microcontroller (0-3.3 V or 0-5 V)
- Pull-up and pull-down resistor networks for digital logic level translation
- Reference voltage generation from a supply rail for comparator and op-amp circuits
- Wheatstone bridge configurations for precision resistance and sensor measurement
- Volume control and signal attenuation in audio circuits using a potentiometer (variable voltage divider)
- Setting feedback ratios in operational amplifier gain circuits
Example
In an NPN transistor amplifier biasing circuit, a voltage divider formed by R1 (47 kOhm, from 12 V supply to base) and R2 (10 kOhm, from base to GND) sets the base bias voltage at Vout = 12 x 10/(47+10) = 2.1 V, establishing the transistor's operating point. The schematic shows the two resistors in a vertical series stack with the horizontal Vout tap connecting to the transistor base terminal. The values and designators R1 and R2 are labelled alongside the resistor symbols.
Key facts
- The Voltage Divider (potential divider) consists of two resistors R1 and R2 in series, with the output taken at their junction; the output voltage is Vout = Vin x R2/(R1 + R2), a formula that must be memorised for circuit analysis.
- The voltage divider formula is exact only for an unloaded output; when a load RL is connected to Vout, the effective shunt impedance is R2 in parallel with RL, reducing Vout below the ideal value if RL is not much larger than R2.
- The symbol is drawn as two resistors (IEC rectangles or ANSI zigzags) stacked vertically in series with Vin at the top, GND at the bottom, and Vout tapping the midpoint node.
- The voltage divider is a passive circuit with no gain greater than 1 (it can only attenuate, never amplify); it is a purely resistive, linear, and frequency-independent network at DC and low frequencies.
- In schematic diagrams, the two resistors are individually designated R1 (upper, series) and R2 (lower, shunt); their values appear next to the symbols and determine the scaling ratio.
- IEC 60617-04 and ANSI Y32.2 / IEEE 315 both draw the voltage divider using standard resistor symbols in a series configuration; no dedicated composite voltage-divider glyph exists in either standard.
- A potentiometer (variable resistor) is the equivalent of a voltage divider with an adjustable tap, allowing continuous variation of Vout between 0 and Vin.
Frequently asked questions
What does the voltage divider symbol look like?
The voltage divider symbol shows two resistors stacked vertically in series: the upper resistor (R1) connects Vin at the top to the midpoint node, and the lower resistor (R2) connects the midpoint to GND at the bottom. A horizontal branch exits the midpoint to form the Vout output terminal, often marked with a junction dot.
What does the voltage divider symbol mean in a circuit diagram?
The voltage divider symbol means two resistors in series are used to produce an output voltage that is a fixed fraction of the input voltage, given by Vout = Vin x R2/(R1 + R2). It is used for biasing, signal scaling, ADC input conditioning, and reference voltage generation.
What is the formula for a voltage divider?
The voltage divider output formula is Vout = Vin x R2/(R1 + R2), where R1 is the series resistor (between Vin and Vout) and R2 is the shunt resistor (between Vout and GND). This formula assumes no load current is drawn from the Vout node.
What is the difference between IEC and ANSI voltage divider symbols?
IEC 60617 draws resistors as filled rectangles, so the IEC voltage divider shows two rectangle resistors in series. ANSI Y32.2 / IEEE 315 draws resistors as zigzag lines, so the ANSI voltage divider shows two zigzag resistors in series. The circuit topology, output tap, and function are identical in both standards.
What is a potential divider and is it the same as a voltage divider?
Yes. Potential divider and voltage divider are synonymous terms for the same two-resistor series circuit with a tapped midpoint output. Potential divider is more commonly used in British and IEC-influenced technical literature; voltage divider is more common in American and IEEE-influenced usage.
Why does the voltage divider output change when a load is connected?
When a load resistor RL is connected to Vout, it appears in parallel with R2, reducing the effective shunt impedance to R2 x RL/(R2 + RL). This is smaller than R2 alone, so the output voltage falls below the ideal unloaded value. To minimise loading error, the load impedance should be at least 10 times greater than R2.
What standard defines the voltage divider circuit symbol?
IEC 60617-04 defines the individual resistor symbols used in the voltage divider; ANSI Y32.2-1975 / IEEE 315-1975 defines the ANSI resistor symbols. Neither standard defines a combined composite voltage-divider glyph; the circuit is drawn using standard resistor symbols in a series topology with a labelled output tap.
Place the Voltage Divider symbol on a wiring diagram or schematic in the free online circuit diagram maker — no download required.