A wilson current mirror is a threeterminal circuit fig. Chapter 16 analog integrated circuits chapter outline 16. Ee105 fall 2014 microelectronic devices and circuits. Pdf widlar current mirror design using bjtmemristor. Introduction to electronics xvi 1 i use the word supposedly because, in my view, the official rewards for textbook authoring fall far short of what is appropriate and what is achievable through an equivalent. In the reference current generating circuit x1, the nchannel mos transistors m11 and m12 constitute a widlar current mirror circuit. The focus of analysis were a power dissipation, a total harmonic distortion and a chipsurface. Pdf this paper investigates the state of the art compensation. Basic current mirror basically, current mirrors cms are used to mirror a reference current multiple times from one designated source into another consuming circuits. V d bipolar diode exponential diode connected transistor quadratic v t v d i d v ds v gs v t after we reach the point v d v t, the transistor will always be in sat. Important attributes for current sources include high output resistance with a wide range of voltage compliance and rejection of external variations such as power supply or temperature. This additional component forces the currents in the two branches of the circuit to be unequal. Repeat the same procedure you followed for the simple mirror circuit.
Current mirror circuits generally consist two main transistor, although other devices such as fets can be used. The main design criteria for this project is to achieve psrr above 60db and a variation less than 3% resulting from temperature changes. The circuit consists of an input diff amp and four wilson current mirrors. The basic parameter that describes the functionality of a current. A current mirror circuit has lots of primary and secondary dependencies and that is the main concern to characterize current mirror circuit. We saw that circuit when looking inside the 741 op amp. Current mirror circuit designs using bjt and mosfet. The above circuit does pose its own voltage headroom limitation. The output current in each is the collector current io. Reference has been moved so link is no longer valid. Eecs140 analog circuit design lectures on current sources simple source cont. This is why these circuits are called current mirrors. This didactic study consists of a detailed analysis followed by a stepbystep design procedure that takes. 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.
Specifics of using current mirrors for highside current measurements in detector power supplies george mitev mitev. Media in category current mirror circuits the following 56 files are in this category, out of 56 total. What is the best one between wilson current source or. An important feature of the current mirror is a relatively high output resistance which helps to.
The widlar circuit may be used with bipolar transistors, mos transistors, and even. Now wilson current mirror is less dependent on beta values meaning it is less dependent on transistor parameters but o. Current mirrors consist of two branches that are parallel to each other and create two approximately equal currents. The output impedance of a widlar current mirror is approximately, where. What are the advantages and disadvantages of using an. In the video, the programmed voltage across q2s collector is reflecting across the q3 collector. A low voltage selfbiased and bulkdriven mosfet wilson current mirror circuit 1shobhna, 2mrs. Widlarwidlar voltagereading temperature sensor request pdf.
This didactic study consists of a detailed analysis followed by a stepby. Widlar current mirrors,wilson current mirrors and cascoded current mirrors. A low voltage selfbiased and bulkdriven mosfet wilson. In this circuit, if mosfets m1 and m2 operate in saturation region, output current i out is proportional to input current i in by the ratio of their aspect ratios. To get a good insight of current mirrors current sources read the manual. Like the wilson and widler current mirror circuits, this new current mirror can be used as a low current biasing circuit. Widlar mirror topology is one that shows up in numerous monolithic ics. A negative feedback loop is created to ensure that the current does not change with pvt variations, thereby making it a good current source. Higher values are not easily accomodated without further circuit changes, as already with 620 the. Instead of the large resistors required to create small currents, the widlar. Widlar current mirror design using bjtmemristor circuits. The analysis has been performed by comparing a modified configuration with a simple circuit of widlar cm. The current mirror is used to provide bias currents and active loads to circuits. A current mirror is a circuit block which functions to produce a copy of the current flowing into or out of an input terminal by replicating the current in an output terminal.
Analysis and design of analog integrated circuits 4th ed. Since multistage amplifier systems often have high gain, bias currents must be small. Dawson page 3 notice how this technique solves a thorny problem for using transistors as a current source. Iowa state university ames, ia 50011, usa dallas semiconductor corp. The circuit is exactly the same as the basic current mirror circuit using two bjt transistors. 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. Figure 3 shows that even the highest resistor value of 620 gives a slight advantage over the second largest 430. A novel tuning principle for simple gyratorbased cmos active inductor ai circuit is presented. The current mirrors are particularly useful for the distribution of bias currents in larger circuits. If too much current is being output 25ma, the voltage drop across r6, r7 will turn q15, q21 on to bleed off the current via q22, q24 current mirror. Short circuit protection q15, q21 are normally off. The only difference between the two circuits is the introduction of an emitter resistor. 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.
I ran it in pspice, and did a sweep of load resistors from 1 to 2. Various types of current mirror circuits are discussed in sectionii,sectioniii describes low voltage bulkdriven mosfet current mirror for cmos technology. When using discrete transistors, you may glue their cases together to do this. Ee105 fall 2014 microelectronic devices and circuits prof. A current mirror circuit, mirror or copy the input current of one active device to the other.
Summing currents at the node where iref enters the circuit yields. Also, when compared with basic current mirror, improved one consumes only 14th of the power consumed by the basic current mirror. Current mirrors ii ele 344 university of rhode island, kingston, ri 028810805, u. Files are available under licenses specified on their description page. In the final section, we saw some examples of how current mirrors are incorporated into analog integrated circuits.
Robert widlar, 53, designer of computer circuits the new. Chapter 16 analog integrated circuits 1179 a b legends of analog design a robert j. For the love of physics walter lewin may 16, 2011 duration. Current sources and active loads university of north. 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.
Current mirrors are basic building blocks of analog design. Compliance voltage for current mirrors a measure of the minimum load or output voltage for which the current mirror can maintain a constant current. 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. The rest of the mirror circuit acts as a feedback to control it. To best understand this important circuit building. A current mirror is one where two or more branches carry identical currents. Widlar current source the widlar current source, a variation of the simple current mirror, was advanced by bob widlar in the mid 1960s. This new mirror is well suited for low current biasing applications. An ai using a conventional current mirror ccm and widlar current source have been implemented in the 0. An important feature of the current mirror is a relatively high output resistance which helps to keep the output current constant regardless of load conditions. An operation of the reference current generating circuit x1 will be described below. Each has different advantages and their uses are for different purposes.
Current mirror circuit 2 wilson current mirror analog electronics83 by sahav singh yadav duration. All structured data from the file and property namespaces is available under the creative commons cc0 license. A proper current mirror circuit can be characterized using three specifications. 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. Replicate reference current at various places required. The resulting class of subcircuits is called current mirrors. Something special happens if one resistor is zero, but the other is not. The current mirror circuit gains its name because it copies or mirrors the current flowing in one active device in. 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. Tunable cmos active inductor using widlar current source. The method makes use of widlar current source to enhance the quality factor. Summary of key concepts voltage source easily synthesized from reference current source using mosfet in diode configuration current source easily synthesized from current source using current mirror circuit.
Transistor current mirror circuit electronics notes. Some current mirror circuits may use more than two transistors to enable the level of performance to be improved. Us20110221517a1 reference current generating circuit. May 22, 2002 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 amplifiers, and other such circuits. Index termscurrent mirror, widlar current source, bjtmemristor circuit, power analysis, noise analysis, total harmonic distortion. Widlar current mirror bipolar junction transistor electrical circuits.
In case of identical mosfets, i in i out and the circuit simply replicates or mirrors the input current at its output terminal and hence the name current mirror. Wilson and widlar current mirroring techniques february 2020 to improve the output of basic current mirror circuit, we will discuss to popular current mirror techniques wilson current mirror circuit and widlar current source circuit. Twobjt current source figure 3 shows npn and pnp twotransistor bjt current sources that are simpler to design. Equivalent circuits of the mosfet cascode current mirror for determining r o 4. Modify the simple mirror circuit by adding the base current compensation transistor q 3 as shown below. Q1s emitter voltage must be carefully controlled to get low drift. Ec8453 important questions linear integrated circuits. The widlar circuit may be used with bipolar transistors, mos transistors, and. 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. It will start at an introductory level and will bring the reader right up to the stateoftheart.
The performance of the tunable ai using widlar current source are compared with the same using a simple current mirror. 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. This paper presents a description of basic current mirror cm, widlar current mirror, fourth circuit element. Another excellent current mirror circuit is the widlar current source circuit, invented by bob widlar the circuit is exactly the same as the basic current mirror circuit using two bjt transistors. May 27, 2019 a current mirror circuit has lots of primary and secondary dependencies and that is the main concern to characterize current mirror circuit. Transistors do not have to be matched to make a current mirror. It comprises two transistors, one of which has the base and collector connected and the other does not. Wilson current source is a current mirror while widlar current source is independent from reference current. Another excellent current mirror circuit is the widlar current source circuit, invented by bob widlar. The basic circuit of the transistor current mirror is shown in the diagram below. Ive designed this widlar current source to deliver 5ma of current. A widlar mirror named after robert widlar can be used when low levels of output currents are needed.
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 the widlar circuit may be used with bipolar transistors, mos transistors, and even vacuum tubes. Specifics of using current mirrors for highside current measurements in detector power supplies george mitev mitev abstract in this article are described novel, current mirror based, highside current measurement circuits for ionizing radiation detector power supplies. A widlar current source is used in analog integrated circuit design to produce a small driving current without the use of large resistors. Pdf eliminating the early effect in the wilson current mirror.
Widlar, a prolific designer of integrated circuits and a colorful personality in the silicon valley, died last wednesday. One kind of a reference voltage generating circuit includes a constant current circuit, a current mirror circuit, and a load resistor. After some careful analysis of the widlar current source, i came to the conclusion that the this circuit is called source rather than mirror because the two currents on each branch of the circuit do not match. The implementation of the current mirror circuit may seem simple but there is a lot going on. Ec8453 important questions linear integrated circuits i describe about output offset voltage. The goal of this activity is to study the bjt current source or current mirror. Current mirrors current mirrors are important blocks in electronics. Passive and active current mirrors analog circuit design 51 chingyuan yang ee, nchu overview zreading b.
Designing the widlar current mirror designing the widlar. A wilson current mirror or wilson current source, named after george wilson, is an improved mirror circuit. Transistors in a current mirror circuit must be maintained at the same temperature for precise operation. Specifics of using current mirrors for highside current. They are widely used in several applications and chips, the operational amplifier being one of them. Index terms current mirror, widlar current source, bjtmemristor circuit, power analysis, noise analysis, total harmonic distortion. An example application of the current mirror is the transconductance op amp.
Temperature independent band gap reference voltage using. A brief introduction of wilson and widlar current sources and the steps to carry out the lab are given here. This lecture deals with the design of current mirrors as both bias elements and signal processing. The pchannel mos transistors m to m15 constitute a typical linear current mirror circuit whose input side is the transistor m14. The mirror works by establishing a vbe on the input transistor that will provide a collector current equal to the input current, that is to say that the vbe developed is appropriate for that particular transistor at whatever input current is supplied, it follows that if another transistor at the same temperature and with the same base area is connected base emmiter it also will have the same.
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