Voltage ladder
Encyclopedia
A voltage ladder is a simple electronic circuit
consisting of several resistor
s connected in series with a voltage
placed across the entire resistor network. Voltage ladders are useful for providing a set of successive voltage references, for instance for a Flash analog-to-digital converter
.
occurs across each resistor in the network causing each successive "rung" of the ladder (each node of the circuit) to have a higher voltage then the one before it. Ohm's law
can be used to easily calculate the voltage at each node. Since the ladder is a series circuit, the current
is the same throughout, and is given by the total voltage divided by the total resistance (V/Req), which is just the sum of each series resistor in the ladder. The voltage drop across any one resistor is now given simply by I*Rn, where I is the current calculated above, and Rn is the resistance of the resistor in question. The voltage referenced to ground
at any node is simply the sum of the voltages dropped by each resistor between that node and ground. Alternatively, you can use voltage division
to determine node voltages without having to calculate the current directly. By this method, the voltage drop across any resistor is V*Rn/Req where V is the total voltage, Req is the total (equivalent) resistance, and Rn is the resistance of the resistor in question. The voltage of a node referenced to ground is still the sum of the drops across all the resistors, but it's now easier to consider all these resistors as a single equivalent resistance RT, which is simply the sum of all the resistances between the node and ground, so the node voltage is given by V*RT/Req.
Electronic circuit
An electronic circuit is composed of individual electronic components, such as resistors, transistors, capacitors, inductors and diodes, connected by conductive wires or traces through which electric current can flow...
consisting of several resistor
Resistor
A linear resistor is a linear, passive two-terminal electrical component that implements electrical resistance as a circuit element.The current through a resistor is in direct proportion to the voltage across the resistor's terminals. Thus, the ratio of the voltage applied across a resistor's...
s connected in series with a voltage
Voltage
Voltage, otherwise known as electrical potential difference or electric tension is the difference in electric potential between two points — or the difference in electric potential energy per unit charge between two points...
placed across the entire resistor network. Voltage ladders are useful for providing a set of successive voltage references, for instance for a Flash analog-to-digital converter
Flash ADC
A Flash ADC is a type of analog-to-digital converter that uses a linear voltage ladder with a comparator at each "rung" of the ladder to compare the input voltage to successive reference voltages...
.
How it works
A voltage dropVoltage drop
Voltage drop is the reduction in voltage in the passive elements of an electrical circuit. Voltage drops across conductors, contacts, connectors and source internal resistances are undesired as they reduce the supplied voltage while voltage drops across loads and other electrical and electronic...
occurs across each resistor in the network causing each successive "rung" of the ladder (each node of the circuit) to have a higher voltage then the one before it. Ohm's law
Ohm's law
Ohm's law states that the current through a conductor between two points is directly proportional to the potential difference across the two points...
can be used to easily calculate the voltage at each node. Since the ladder is a series circuit, the current
Electric current
Electric current is a flow of electric charge through a medium.This charge is typically carried by moving electrons in a conductor such as wire...
is the same throughout, and is given by the total voltage divided by the total resistance (V/Req), which is just the sum of each series resistor in the ladder. The voltage drop across any one resistor is now given simply by I*Rn, where I is the current calculated above, and Rn is the resistance of the resistor in question. The voltage referenced to ground
Ground (electricity)
In electrical engineering, ground or earth may be the reference point in an electrical circuit from which other voltages are measured, or a common return path for electric current, or a direct physical connection to the Earth....
at any node is simply the sum of the voltages dropped by each resistor between that node and ground. Alternatively, you can use voltage division
Voltage divider rule
In electronics, a voltage divider is a simple linear circuit that produces an output voltage that is a fraction of its input voltage...
to determine node voltages without having to calculate the current directly. By this method, the voltage drop across any resistor is V*Rn/Req where V is the total voltage, Req is the total (equivalent) resistance, and Rn is the resistance of the resistor in question. The voltage of a node referenced to ground is still the sum of the drops across all the resistors, but it's now easier to consider all these resistors as a single equivalent resistance RT, which is simply the sum of all the resistances between the node and ground, so the node voltage is given by V*RT/Req.