Analysis of the importance of reference voltage source

Many people know the reference voltage, so what is its role? Since it is everywhere, let’s take a look at how important the reference voltage is. Do we use it every day? Whether it is a car or a computer, as long as it is an electronic product, it must interact with "reality" in some way. This combination can measure (characteristics: speed, pressure, length, temperature) and map it to electronic products as (voltage). This requires a measurement standard, and the standard we are talking about is the reference voltage.

Reference voltage source? Where will it be used? What role does it play and what can it help us do? Let’s learn more about it!

definition:

The reference voltage source is an extremely important component of contemporary analog integrated circuits. It provides a reference voltage for series voltage stabilizing circuits, A/D and D/A converters, and is also the regulated power supply or excitation source for most sensors. In addition, the reference voltage source can also be used as a standard battery, a scale standard for instrument gauges, and a precision current source.

A voltage reference is simply a circuit or circuit element that provides a known potential whenever the circuit requires it. This could be minutes, hours or years. If the product needs to collect relevant real-world information, such as battery voltage or current, power consumption, signal size or characteristics, fault identification, etc., then the relevant signal must be compared to a standard. Every comparator, ADC, DAC, or detection circuit must have a voltage reference to do this. Any signal can be accurately quantified by comparing the target signal to a known value.

ideal voltage reference source

An ideal voltage reference should have perfect initial accuracy and remain stable as load current, temperature, and time change. In practical applications, designers must make trade-offs among indicators such as initial voltage accuracy, voltage temperature drift, hysteresis, and ability to source/sink current, quiescent current (i.e., power consumption), long-term stability, noise, and cost.

Type of reference source

Two common references are Zener and bandgap references. Zener reference sources usually use a two-terminal parallel topology; bandgap reference sources usually use a three-terminal series topology.

Method to realize

1. Resistor voltage division:

It can only be used as the bias voltage of the amplifier or to provide the operating current of the amplifier. This is mainly because it has no voltage stabilizing effect on its own, so the stability of the output voltage completely depends on the stability of the power supply voltage.

2. Ordinary forward diode

A constant reference voltage that does not depend on the power supply voltage, but its voltage stability is not high, and its temperature coefficient is negative, about -2mV/℃

3. Zener diode

It can overcome some shortcomings of the forward diode as a reference voltage, but its temperature coefficient is positive, about +2mV/℃

4. Temperature compensated Zener diode

It is small in size, light in weight, simple in structure and easy to integrate; but it has shortcomings such as high noise, weak load capacity, poor stability, high reference voltage, and poor adjustability. This voltage reference is not suitable for portable and battery-powered applications.

5. Bandgap reference source (implemented using CMOS, TTL and other technologies)

There are many types of reference voltage sources made using semiconductor integrated circuit technology, such as deeply buried zener tube integrated reference sources, bipolar transistor integrated bandgap reference sources, CMOS integrated bandgap reference sources, etc. "Bandgap reference source" is a new type of device that appeared in the early 1970s. Its advent has brought a new leap in the indicators of reference devices. Because the bandgap reference source has high accuracy, low noise, and advantages, it is widely used in voltage regulators, data converters (A/D, D/A), integrated sensors, amplifiers, etc., and as a separate precision voltage reference component. , low temperature drift and many other micro-power operational amplifiers.

Summarize:

The difficulty of any system design lies in the balance and trade-off among many factors such as cost, volume, accuracy, power consumption and so on. All relevant parameters need to be considered when selecting the best reference source for a specific design. Interestingly, many times using more expensive components makes the overall system cost lower because it reduces the cost of compensation and calibration during the manufacturing process. This is the importance of the reference voltage, which requires everyone to continuously accumulate it.