Widlar current mirror design using bjtmemristor circuits arxiv. This didactic study consists of a detailed analysis followed by a stepby. Design a widlar current source that produces an output current of. China 2 school ofelectric and information engineering, wuhan institute oftechnology, wuhan 430073, china email. Tunable cmos active inductor using widlar current source. Iowa state university ames, ia 50011, usa dallas semiconductor corp. The bjts, q 1 and q 2 comprise a matched monolithic pair, fabricated close together on the same ic chip, such as is available with a bjt array. Ive designed this widlar current source to deliver 5ma of current. The ref200 combines three circuit buildingblocks on a single monolithic chip. The cascode and wilson current q1 q2q3 q4 figure 16. International journal of electrical engineering education 404 designing the widlar current mirror bryan hart leigh on sea, essex, uk abstract the widlar current mirror, a widely used integrated circuit configuration, normally receives only a superficial treatment in electronics texts. This didactic study consists of a detailed analysis followed by a stepbystep design procedure that takes. Circuits dealing with signals free to vary from zero to full power supply voltage. Widlar current source the widlar current source differs from the basic current mirror in one important way a resistor r 2 is added to the emitter circuit of transistor q 2.
Designing the widlar current mirror designing the widlar. The free holes wish to combine with the free electrons. Something special happens if one resistor is zero, but the other is not. The sections are dielectrically isolated, making them completely independent.
The current mirror starts working only when v in exceeds the v be on of the mirror transistors, so there is a non. Temperature independent band gap reference voltage using. China 2 school ofelectric and information engineering, wuhan institute oftechnology, wuhan 430073, china. This is the widlar current mirror, which has some applications as a crude bias reference the output is still dependent on the input, but it varies logarithmically as vbe vs.
Types of mirrors there are three types of current mirrors that will be discussed throughout this article. Index termscurrent mirror, widlar current source, bjtmemristor circuit, power analysis, noise analysis, total harmonic distortion. The current mirror is an important analog building block that finds application in. A novel bandgap reference for minimizing currentmirror mismatch. The ds3920 precision current mirror is designed for avalanche photodiode apd and pin photodiode biasing and monitoring applications. Current sources and active loads university of north. The connection to the base of t 3 and t 4 and the t 8 t 9 mirror, establish the currents in the differential pair through a feedback loop. A 100a current source is tied to the mirror common. Another variation of the basic current mirror circuit is referred to as the wilson mirror or wilson current mirror. It may be used as a wilson current source by applying a constant bias current to the input branch as in fig. An ai using a conventional current mirror ccm and widlar current source. Current mirrors take advantage of the relationship between vbe and ic. Figure 3 shows that even the highest resistor value of 620 gives a slight advantage over the second largest 430.
Index termscurrent mirror, widlar current source, bjt memristor circuit, power analysis, noise analysis, total harmonic distortion. To get a good insight of current mirrors current sources read the manual. Structure and characteristics of the bjt widlar current mirror. The performance of the tunable ai using widlar current source are compared with the same using a simple current mirror. This work was supported, in part, by dallas semiconductor corp.
Circuit bias currents are, as usual, provided by a set of current mirror configurations. The simple two transistor implementation of the current mirror is based on the fundamental relationship that two equal size transistors at the same temperature with the same v gs for a mos or v be for a bjt have the same drain or collector current. The widlar source is an important analog building block. A current mirror is a transistor circuit that regulates the current through a load resistance, the regulation point is set by a simple resistor adjustment. Oct 09, 2019 if you decide for the widlar basic twotransistor design, its important to rely on matched pairs built on purpose, like the bcv61. Widlar current source the widlar current source, a variation of the simple current mirror, was advanced by bob widlar in the mid 1960s. This is particularly important because it is difficult to produced large resistors on chip that have good tolerances, meaning that it is very difficult to get predictable, reliable currents using large. Implementation and applications of current sources and. Introduction to electronics ii dedication human beings are a delightful and complex amalgam of the spiritual, the emotional, the intellectual, and the physical. Pdf widlar current mirror design using bjtmemristor. This additional component forces the currents in the two branches of the circuit to be unequal.
The current i 2 is going to depend on the value of r 3, and for all weve learnt this type of configuration is going to allow the current i 2 to be less than or equal to the reference current i 1, not higher than the reference. A widlar current source is a modification of the basic two transistor current mirror that incorporates an emitter degeneration resistor for only the output transistor, enabling the current source to generate low currents using only moderate resistor values. Since a current mirror output must equal its input, 50a flows in the input to ground, and the output is a 50a current sink. E 5 hich is called the proportional to absolute temperature ptat current. May 17, 2018 put a resistor under the emitter of the diodeconnected reference transistor. Designing the widlar current mirror free download the widlar current mirror, a widely used integrated circuit configuration, normally receives only a superficial treatment in electronics texts. Pdf the decision for most the appropriate current mirror topology when designing.
Zetex zds1009 current mirror datasheet battery chargers dc motor control outrush current sensing inrush current sensing wide operating voltage range excellent temperature tracking characteristics simplifies circuit implementation only four connections required created date. Current and voltage sources 1 analog design for cmos vlsi systems franco maloberti current mirrors a current mirror gives a replica attenuated or amplified, if necessary of a bias or signal current. Widlar current mirrors widlar current mirrors resemble classical mirrors but the gatesource voltage of the input transistor in diode connection is distributed between the vgs of the output transistor and a series degeneration resistor. Widlar current mirror design using bjtmemristor circuits. Thus, the current mirror circuit acts to regulate current at a value set by the potentiometer, without regard to load resistance. Chapter 16 analog integrated circuits chapter outline 16. True current sources are a rarity compared to voltage sources, and therefore we must generally devise some form of currentregulation circuit to use in conjunction with available voltage sources in order to mimic a true current source. What is the reference current needed to produce the 1ma output current.
Transistor current mirror circuit electronics notes. Passive and active current mirrors analog circuit design 51 chingyuan yang ee, nchu overview zreading b. Pdf this paper investigates the state of the art compensation. The current mirror is used to provide bias currents and active loads to circuits. Specifics of using current mirrors for highside current. This module explains how to do this using transistors. The widlar source was designed by and named for bob robert widlar, who worked for national semiconductor and produced a number of very profitable designs.
A ptat current can be copied from the current mirror and can be adjusted by changing the width of m12 or the resistance of r1. The mirrored current is a precise copy of the input current. If you decide for the widlar basic twotransistor design, its important to rely on matched pairs built on purpose, like the bcv61. I ran it in pspice, and did a sweep of load resistors from 1 to 2. Higher values are not easily accomodated without further circuit changes, as already with 620 the.
The widlar circuit may be used with bipolar transistors, mos transistors, and. T 11, t 12 and r 5 establish the value of the current that is mirrored by t 10. Ref200 dual current source and current sink datasheet rev. This transistor, shown as tr3 in the diagram keeps the collector of tr1 at a voltage equivalent to two diode drops below the rail voltage vcc. Transistors in a current mirror circuit must be maintained at the same temperature for precise operation. Pdf analysis, simulation and circuit implementation of a precise. With a constant base current and a nearly constant.
Put a resistor under the emitter of the diodeconnected reference transistor. The schematic of the circuit is illustrated in figure 6. This paper presents a description of basic current mirror cm, widlar current mirror, fourth circuit element memristor and an analysis of widlar configuration with integrated memristor. A novel bandgap reference for minimizing currentmirror. This lecture deals with the design of current mirrors as both bias elements and signal processing. Jan 30, 2017 structure and characteristics of the bjt widlar current mirror. If compliance closer to the negative rail is needed for either. A wilson current mirror is a threeterminal circuit fig. A read is counted each time someone views a publication summary such as the title, abstract, and list of authors, clicks on a figure, or views or downloads the fulltext. There, the blue current mirror circuit is a widlar current mirror. A brief introduction of wilson and widlar current sources and the steps to carry out the lab are given here. Passive and active current mirrors analogcircuit design 51 chingyuan yang ee, nchu overview zreading b.
The focus of analysis were a power dissipation, a total harmonic distortion and a chipsurface. A negative feedback loop is created to ensure that the current does not change with pvt variations, thereby making it a good current source. Basic current mirror basically, current mirrors cms are used to mirror a reference current multiple times from one designated source into another consuming circuits. Read on wikipedia edit history talk page print download pdf.
When using discrete transistors, you may glue their cases together to do this. Widlar basics the widlar current mirror is shown in fig. A wilson current mirror or wilson current source, named after george wilson, is an improved mirror circuit. Ib, which is better than a resistor which varies proportionally and computation element the exponent of the sum of two logs is the product of those numbers, i. The only difference between the two circuits is the introduction of an emitter resistor. As involvement of emitter resistor in current mirrors has certain drawbacks like restricting the output voltage range to a lower valuethus in order to cancel the draw back of emitter resistors they say to use a widlar current mirror widlar current mirror is designed to provide very small. The only progress ive been able to make is through kvl that r 1 is approximately 9. Transistor current mirror circuits are often used within integrated circuits as well. Instead of the large resistors required to create small currents, the widlar. The rest of the mirror circuit acts as a feedback to control it. Pdf compensation in mos current mirror circuits researchgate. We saw that circuit when looking inside the 741 op amp.
To best understand this important circuit building. The widlar circuit may be used with bipolar transistors, mos transistors, and even. The implementation of the current mirror circuit may seem simple but there is a lot going on. The feedback can be connected in series with the load current feedback or in parallel voltage feedback. The analysis has been performed by comparing a modified configuration with a simple circuit of widlar cm. Voltage references and biasing stanford university. Lesson 1 voltage, current, resistance engineering circuit. Also, because the current sources are twoterminal devices, they can be used equally well as current sinks. For a 50a current sink, use the circuit shown in figure 4. It is a widlar mirror without an emitter degeneration resistor in the follower output transistor. The voltage difference between the two pn junctions is the positivetc voltage. Since multistage amplifier systems often have high gain, bias currents must be small.
The device offers a current clamp to limit current through the apd and a. Edn use a current mirror to control a power supply. May 22, 2002 a widlar current source is used in analog integrated circuit design to produce a small driving current without the use of large resistors. Thus, as in the opamp version of this circuit, the diode provides its own bias current. Within the circuit, a third transistor is introduced.
Widlarwidlar voltagereading temperature sensor request pdf. Zds1009 current mirror datasheet diodes incorporated. To improve the output of basic current mirror circuit, we will discuss to popular current mirror techniques wilson current mirror circuit and. Introduction to electronics an online text electrical and computer. May 05, 2015 as involvement of emitter resistor in current mirrors has certain drawbacks like restricting the output voltage range to a lower valuethus in order to cancel the draw back of emitter resistors they say to use a widlar current mirror widlar current mirror is designed to provide very small. The diodebiased current mirror current ratio reference current 1 output resistance 1 compliance range 2 using a mirror to bias an amplifier 2 wilson current mirror 3 current ratio 3. A widlar current source is a modification of the basic twotransistor current mirror that incorporates an emitter degeneration resistor for only the output transistor, enabling the current source to generate low currents using only moderate resistor values. An example application of the current mirror is the transconductance op amp. When combined with other blocks such as the differential pair and the current mirror, it can be used in the design of operational amplifiers, operational transconductance. The device offers a current clamp to limit current through the apd and a current mir.
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