Voltage Reference Circuits | Analog Circuits - Electronics and Communication Engineering (ECE) PDF Download

Voltage Reference Circuits

A voltage reference is an electronic device which produces a constant voltage regardless of the loading on the device, temperature changes, passage of time and power supply variations.
The voltage reference circuit most commonly used in integrated circuits is the bandgap voltage reference.
A bandgap voltage reference uses analog circuits in order to add a multiple of the voltage difference between two bipolar junctions biased at different current densities to the voltage developed across a diode.
The diode voltage has a negative temperature coefficient and the junction voltage difference has a positive temperature coefficient. When added in the proportion which is required in order to make these coefficients cancel each other, the resultant constant value is a voltage which is equal to the bandgap voltage of the semiconductor.

Types of Voltage References:

  • There are several different kinds of voltage references. Most common types categorized by type, tolerance, rated voltage, reference voltage, forward (drive) current, rated current, quiescent current and packaging type. The most common sizes for tolerance are ± 2%, ± 1% and ± 0.5%.
  • Voltage references have a major impact on the performance and accuracy of analog systems.
  • A 5 mV tolerance on a 5 V reference corresponds to 0.1% absolute accuracy which is only 10-bit accuracy.
  • For a 12-bit system, choosing a reference that has a 1 mV tolerance may be far more cost effective than performing manual calibration, while both high initial accuracy and calibration will be necessary in a system making absolute 16-bit measurements.
The document Voltage Reference Circuits | Analog Circuits - Electronics and Communication Engineering (ECE) is a part of the Electronics and Communication Engineering (ECE) Course Analog Circuits.
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FAQs on Voltage Reference Circuits - Analog Circuits - Electronics and Communication Engineering (ECE)

1. What is a voltage reference circuit?
Ans. A voltage reference circuit is a circuit that produces a stable and accurate voltage output regardless of changes in input voltage or load conditions. It is commonly used in electronic devices to provide a precise reference voltage for various purposes such as calibration, biasing, or voltage regulation.
2. What are the different types of voltage reference circuits?
Ans. There are mainly two types of voltage reference circuits: series voltage references and shunt voltage references. In a series voltage reference, the reference voltage is connected in series with the load, while in a shunt voltage reference, the reference voltage is connected in parallel with the load. Both types have their advantages and are used based on the specific requirements of the application.
3. How does a voltage reference circuit work?
Ans. A voltage reference circuit typically consists of a stable voltage source, a voltage divider network, and an output buffer. The stable voltage source generates a reference voltage, which is divided down by the voltage divider network to obtain the desired output voltage. The output buffer ensures that the reference voltage is isolated from the load and provides a low-impedance output to drive other circuitry.
4. What are the key parameters to consider when selecting a voltage reference circuit?
Ans. When selecting a voltage reference circuit, some key parameters to consider include accuracy, temperature coefficient, stability, noise performance, and load regulation. Accuracy refers to how closely the output voltage matches the desired reference voltage. Temperature coefficient measures the change in output voltage with temperature. Stability refers to the ability of the circuit to maintain its output voltage over time. Noise performance determines the amount of unwanted electrical noise introduced into the reference voltage. Load regulation measures how well the circuit maintains its output voltage when the load current changes.
5. What are some common applications of voltage reference circuits?
Ans. Voltage reference circuits find applications in a wide range of electronic devices and systems. Some common applications include analog-to-digital converters (ADCs), digital-to-analog converters (DACs), voltage regulators, precision measurement instruments, sensor interfaces, and voltage-controlled oscillators (VCOs). In these applications, a stable and accurate reference voltage is essential for ensuring proper functionality and performance of the circuits or systems.
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