What Is a Linear Integrated Circuit?

An integrated circuit based on an amplifier. Since the information processed involves continuously changing physical quantities (analogs), this circuit is also called an analog integrated circuit.

Chinese name: Linear integrated circuit
Foreign name: linearintegrated circuit

Nature: integrated circuit
Including: Continuously changing physical quantity
status quo: There are many types of linear integrated circuits

Introduction to Linear Integrated Circuits

An integrated circuit based on an amplifier. In the early 1960s, the first simple integrated amplifier was made of semiconductor silicon. The term "linear" was used to indicate that the amplifier's response to the input signal was usually linear. Later, this circuit included oscillation

Linear integrated circuit Controllers, timers, and data converters, as well as many non-linear circuits and circuits that combine digital and linear functions. Since the information processed involves continuously changing physical quantities (analogs), this circuit is also called an analog integrated circuit.

Development of linear integrated circuits

Compared with discrete component circuits, integrated circuits have several advantages in their design. Since all devices are manufactured simultaneously on a small chip, their characteristics are very consistent, and the component parameters have high proportional accuracy. Linear circuits usually require different types of devices in one circuit, so it is difficult to integrate, and the initial development is slow. In 1964, a lateral PNP transistor was made, which played an important role in the development of linear integrated circuits. This uses a ring-shaped P-type diffusion region as the collector and another P-type diffusion in the ring

Linear integrated circuit Area as the emitter. This structure can be manufactured at the same time as a standard NPN transistor, creating conditions for the realization of a bipolar complementary circuit. In 1966, the first high-performance general-purpose operational amplifier was introduced. It is flexible in application and small in size, which promotes the rapid development of electronics. In the late 1960s, various linear circuits were widely used. In the 1970s, various high-precision digital-to-analog and analog-to-digital converters became key devices for digital technology and microprocessors to be popularized and applied in the fields of information processing and process control.

A new development in linear circuits is the use of MOS processes to make audio filters. Its principle is the switched capacitor method, which uses switches to alternately connect capacitors to different voltage nodes in the circuit to transfer charge, thereby generating equivalent resistance. This technique is particularly suitable for MOS processes (see Switched Capacitor Filters). On the other hand, due to the application of analog sampling technology, high-stability operational amplifiers and high-precision digital-to-analog and analog-to-digital converters have been produced using the MOS process. The combination of these two technologies opens the way for large-scale integration of analog information processing and communication equipment subsystems.

Linear integrated circuit Opened up broad prospects.

Manufacturing process of linear integrated circuit

Most linear integrated circuits are manufactured using standard bipolar processes. In order to obtain high-performance circuits, some modifications or additional manufacturing processes are sometimes made on the basis of standard processes in order to make various components and devices with different performances on the same chip.

Bipolar-field effect compatible technology A technology for making high-performance junction field-effect transistors on bipolar chips. After the NPN tube on the chip is formed, it is doped with two ion implantation techniques to form a low-concentration P-type channel and a high-concentration N + -type gate region (Figure 1).

Linear integrated circuit ). Its grid-drain breakdown voltage can reach 50 to 60 volts, and the pinch-off voltage can be controlled at about 1 volt.

Super-gain transistors are NPN transistors with a common emitter current gain of up to 1000-5000. The base region is made by ion implantation. The doping concentration of the base region is one order of magnitude lower than that of the usual NPN tube base region, and the thickness of the base region is also thinner than that of the usual NPN tube base region (Figure 2).

Subsurface Breakdown Diodes Normal breakdown diodes use the eb junction of an NPN transistor, and its breakdown occurs at the junction surface. The subsurface breakdown diode is a high-concentration P + layer formed by ion implantation under the N + type emission region, and an N + -P + junction is formed deep below the surface (Figure 3). The breakdown voltage of this transistor is lower than the breakdown voltage of the surface junction. The breakdown process is not affected by surface conditions, has low noise, and has good long-term stability.

Linear integrated circuit

Linear integrated circuit high-frequency process

NPN transistors manufactured using standard bipolar processes typically have characteristic frequencies below 1000 MHz

Linear integrated circuit . When high-frequency and high-speed performance is required, microfabrication, thin-layer epitaxy, and shallow junction technology are used. The characteristic frequency of the device can reach 3000 to 5000 MHz. A typical high-frequency process is shown in Figure 4.

High withstand voltage technology Linear bipolar technology can usually achieve withstand voltage performance of 50 ~ 60 volts. In order to obtain the withstand voltage performance of nearly 100 volts or higher, the following measures can be taken: increase the thickness of the N-type epitaxial layer (such as more than 20 microns) to increase the breakdown voltage of the NPN tube; Negative-potential metal interconnects produce parasitic MOS tube effects when they cross lateral PNP transistors; use field electrodes to protect the surface of the isolation junction to avoid excessive concentration of the electric field, which can cause a breakdown voltage (Figure 5).

Linear CMOS technology. This is a very complex and universal compatible technology.

Linear integrated circuit For various bipolar devices and CMOS devices (see complementary metal-oxide-semiconductor integrated circuits). This technology can combine high-performance linear circuits with high-density high-speed logic circuits on a single chip. A linear CMOS process using refractory metal molybdenum as the gate material can make P-channel and N-channel MOS devices on the N-type epitaxial layer of a linear bipolar chip. It only needs 10 photolithography. With two layers of aluminum and molybdenum interconnect. P-channel and N-channel devices can be used alone or in common with an N region (Figure 6).

Precision element passive element resistors usually use semiconductor resistors formed by diffusion layers or ion implantation layers. Making an alloy thin film resistor on a silicon wafer can achieve better temperature stability. However, the accuracy of the resistance values of both is roughly less than 1%. High-precision resistors need to be obtained with the help of various resistance correction techniques. Generally, a pulsed laser beam with a diameter of about 10 micrometers is used. The correction methods include a fusible interconnect method (Figure 7a) and a fused diffusion layer method (Figure 7b).

The mos tube is a metal-oxide-semiconductor field-effect transistor, or a metal-insulator-semiconductor. The source and drain of the MOS tube can be reversed. They are both N-type regions formed in the P-type backgate. In most cases, these two areas are the same, even if the two ends are swapped, it will not affect the performance of the device. Such devices are considered symmetrical.

Linear integrated circuit

Linear integrated circuit circuit type

According to the functions and uses of the circuit, linear integrated circuits can be roughly divided into: general-purpose circuits, including operational amplifiers, voltage comparators, voltage reference circuits, and regulated power supply circuits;

Linear integrated circuit Control and measurement circuits, including timers, waveform generators, detectors, sensor circuits, phase-locked loops, analog multipliers, motor drive circuits, power control circuits, analog switches; data conversion circuits, including digital-to-analog converters , Analog-to-digital converter, voltage-frequency converter; communication circuit, including telephone communication circuit, mobile communication circuit;

Linear integrated circuit Consumer circuits, including television circuits, video recorder circuits, and audio circuits. In fact, there are many other circuits, such as medical circuits such as pacemakers. On the other hand, due to the increasing development of large-scale integration technology and computer-aided design and measurement technology, the design of linear circuits is developing from traditional standard cells to custom integrated circuits with complex functions.

Basic circuit form of linear integrated circuit

There are many types of linear integrated circuits and their designs are different. But some functional unit circuits are used as basic building blocks,

Linear integrated circuit It has been widely used in many circuits.

Linear integrated circuit differential amplifier

Has a symmetrical structure (Figure 8). The transistor pair Q1 and Q2 have the same characteristics and are called differential pairs. Because the constant current source bias is used, if the base current is negligible, the sum of the collector current and it equals I 0, and it has nothing to do with the input voltages U 1 and U 2. The input voltage only changes the bias current I 0 between Q1 and Q2 Distribution in. The relationship between the difference and the input differential voltage U 1- U 2 is given by:

Linear integrated circuit Is a tangent function. When the drive signal is small (| U 1- U 2 | << U T), it is a linear amplifier that can be used to identify the small difference between the two input signals, and it can also be used as a common single-ended input amplifier. When | U 1- U 24 U T, it becomes a limiting amplifier that can be used for phase comparison of two signals. The limiting effect is not due to the saturation of the transistor, but because the constant current bias limits the increase of the collector current, so it has good frequency response characteristics. There are many variations of the difference amplifier. For single-ended output, you can use only a load resistor or a current mirror instead of a resistor (Figure 9). A biased constant current source can sometimes also be replaced with a resistor. In addition, a resistor can be connected in series between the emitters of the two transistors to change the performance of the amplifier.

Op amp is short for operational amplifier. In the actual circuit, a function module is usually combined with the feedback network. Because it was early used in analog computers to implement mathematical operations, it was named "Operational Amplifier" and this name has continued to this day. An op amp is a circuit unit named from the perspective of function. It can be implemented by discrete devices or in semiconductor chips. With the development of semiconductor technology, most op amps now exist in the form of a single chip. There are many types of op amps today, which are widely used in almost all industries.

Linear integrated circuit

Linear integrated circuit analog multiplier

It can accept the input of two analog signals and produce an output signal proportional to its product. Figure 10 shows a Galbert multiplier. The core part is two cross-connected differential transistors composed of Q5 to Q8. Using the above formula, the voltage U 2 = 2 R c I ytanh (U / 2 U T) can be derived. Diodes D1 and D2 are used to generate the inverse hyperbolic tangent

Linear integrated circuit function. The signal currents I x and I y are generated by a voltage-current conversion circuit. If the resistances R x and R y are sufficiently large, then. Therefore, U 2 is proportional to the product of the input voltage U x and U y. The Gailbert multiplier allows the input voltage to have positive or negative polarity, and is therefore commonly referred to as a four-quadrant multiplier. It can be combined with operational amplifiers to perform multiplication and division, square and square root operations, and can also be used for phase detection, frequency doubling and gain control.

Linear integrated circuit bandgap voltage reference

A voltage reference capable of generating a low voltage output (Figure 11). It makes use of an

Linear integrated circuit The voltage is proportional to the negative temperature coefficient of the forward-emitter junction voltage. It is generated by the transistors Q1 and Q2 with different operating current densities on the resistor R2 . The theoretical value of the reference voltage U R that does not change with temperature is about 1.2 volts, which is approximately equal to the forbidden band width of the semiconductor silicon, so it is called an energy gap voltage reference. Due to the processing error of the doping concentration and the geometrical dimensions of the device, the actual available reference voltage temperature coefficient is usually on the order of 10 ppm.

Examples of linear integrated circuits

386 Linear integrated circuit 386 bipolar linear integrated circuit

386 audio power amplifier is mainly used in low-voltage consumer products. To minimize external components, the voltage gain is built into 20. However, by adding an external resistor and capacitor between pins 1 and 8, the voltage gain can be adjusted to any value up to 200. The input is referenced to ground and the output is automatically biased to half the supply voltage. With a 6V supply voltage, its static power consumption is only 24mW, making the 386 particularly suitable for battery-powered applications ^[1] .

Features : 1 Low static power consumption, about 4mA, can be powered by batteries; 2. 2. Wide working voltage range, 4-12V; 3. Fewer peripheral components; 4. The voltage gain is adjustable from 20-200. 5. Low distortion ^[1]

Applications: 1. AM / FM radio audio amplifier; 2. line driver; 3. audio power amplifier for portable recorder; 4. ultrasonic driver; 5. speakerphone system for hands-free telephone; 6. small servo driver; 7. television Audio system; 8, power conversion; ^[1]

Note : 1. Pay attention to the range of output power 2. Pay attention to the matching of the front and back stages 3. Pay attention to the range of distortion ^[1]

34063 34063 Bipolar Linear Integrated Circuit

34063 is a monolithic bipolar linear integrated circuit dedicated to DC. The DC converter control section contains a temperature-compensated bandgap reference source, a duty cycle control oscillator driver and high current output switch, which can output 1.5A. It can use a minimum of external components to form an on-off, step-up converter, step-down converter, and power inverter. The package of 34063 is a plastic double-row 8-lead in-line ^[2] .

Features : It can work at an input voltage of 3.040V, and the short-circuit current limits low quiescent current; the output switching current can reach 1.5A (no external triode); the output voltage is adjustable; the operating oscillation frequency from 100HZ to 100KHZ can constitute a step-up or step-down Reverse power converter ^[2] .