NPN/NPN equivalent: BCM61B 1.2 Features n Current gain matching 1.3 Applications n Current mirror n Differential amplifier 1.4 Quick reference data The current being "copied" can be, and sometimes is, a varying signal current. 0000003654 00000 n circuits, both positive and negative power supplies are used to maintain A larger 0000016205 00000 n NPN/NPN equivalent: BCM61B 1.2 Features n Current gain matching 1.3 Applications n Current mirror n Differential amplifier 1.4 Quick reference data [1] Device mounted on an FR4 Printed-Circuit Board (PCB), single-sided copper, tin-plated and standard footprint. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.) 0000042127 00000 n 0000006855 00000 n A basic observation is that the output transistor is in active mode only so long as its collector-base voltage is non-zero. is not possible to make them the same way or to match their parameters. 0000012168 00000 n The current mirror is used to provide bias current… Products. H��TmL[U~O饥��K�R2zA�1|��`�,5qmג�6�F�ÐD%.����`VJ2�V:pU4B��#�R>&����2q5�H&$$zJ��=7oΓ�y��>�� ���&��������;�c�iS�Lf�٠���? 0000006831 00000 n 44 Generation of IREF for PNP Current Mirror. CH 9 Cascode Stages and Current Mirrors 45 Current Mirror with Discrete Devices Let QREF and Q1 be discrete NPN devices. the emitter circuits, or we can use the cascode mirror configuration. and in many cases compensated in some way. as the reference for the PNP mirror. PNP current mirror is used as a current source load to an NPN amplifier stage. Common Emitter Amplifier - Current Source Biasing 1. In the attachment you can see a PNP current mirror circuit from AoE. This article briefly reviewed BJT operation, then it explored four types of BJT current mirrors: the basic mirror, the mirror with beta helper, the Widlar current source, and the Wilson mirror. In many practical This can be ground 0000109827 00000 n g m = I C /V T is the transconductance. 0000005450 00000 n Can you suggest any topology in order to enhance the current over pnp ? Another way to provide different current magnitudes at different mirror 0000014757 00000 n 0000138949 00000 n Another possibility is that the primary NPN reference may be part of a 1(a) shows the basic npn current mirror. PNP/PNP matched double transistor in a SOT143B small Surface-Mounted Device (SMD) plastic package. 0000004017 00000 n However, we can use both P-channel and N-channel MOSFETs, just as we can use both NPN and PNP transistors in current mirrors. If T1 consists of m transistors and T2 of n transistors, then the output current will be n/m times the input current, as shown in Figure 2b. T3 acts as a regulating valve which increases the current through the current mirror as Input A gets more power while T4 kind of does the opposite by draining current from the mirror with increasing input B power. I B =. The emitters are connected to +V, while the Nov 29, 2015 #1 Hi all, I'm supposed to get 500uA over I2 however due to low beta value of Q4 transistor the current is limited. The two aspects of the Wilson current mirror []. PSpice A/D; PSpice AA; PSpice Systems Option; OrCAD Capture; About PSpice; Resources . Figure 1 shows a schematic for a pnp current mirror. 0000106940 00000 n Q1 collector current will be limited to approximately the amount set by the programming R1. +V1 is not the same as +V2. VBE. FIG. transistors must be constructed horizontally (known as "lateral PNP This does not preclude their Conceptually, an ideal current mirror is simply an ideal inverting current amplifier that reverses the current direction as well. 2. PNP current mirror is used as a current source load to an NPN amplifier stage. In the circuit of Wilson current mirror, the transistor T 3 "moves" one base current from the right to the left leg of the circuit. For non-zero λ, the current ratio will vary slightly due to mismatch in V DS K n1 =K n 'W L! " Although this would seem to be PNP Current Mirror. 0000064157 00000 n We may consider the behavior of Wilson current mirror from two aspects. In fact, however, it works quite well, although in a This tutorial will demonstrate the basic idea of a current mirror which is widely used in integrated circuits. trailer << /Size 1607 /Info 1554 0 R /Root 1561 0 R /Prev 607205 /ID[<574522a2a7cb89b5c44a5f985f099f3a>] >> startxref 0 %%EOF 1561 0 obj << /Type /Catalog /Pages 1557 0 R /Metadata 1555 0 R /Outlines 252 0 R /Threads 1562 0 R /OpenAction [ 1566 0 R /XYZ null null null ] /PageMode /UseNone /PageLabels 1553 0 R /StructTreeRoot 1565 0 R /PieceInfo << /MarkedPDF << /LastModified (D:20070109193425)>> >> /LastModified (D:20070109193425) /MarkInfo << /Marked true /LetterspaceFlags 0 >> >> endobj 1562 0 obj [ 1563 0 R 1564 0 R ] endobj 1563 0 obj << /I << /Title (\001)>> /F 38 0 R >> endobj 1564 0 obj << /I << /Title (\001)>> /F 39 0 R >> endobj 1565 0 obj << /Type /StructTreeRoot /RoleMap 285 0 R /ClassMap 288 0 R /K 1092 0 R /ParentTree 1127 0 R /ParentTreeNextKey 26 >> endobj 1605 0 obj << /S 1088 /O 1289 /L 1305 /C 1321 /Filter /FlateDecode /Length 1606 0 R >> stream Well, the α ratio works similarly: if emitter current is held constant, collector current will remain at a stable, regulated value so long as the transistor has enough collector-to-emitter voltage drop to maintain it in its active mode. Granted Application number DE19782846202 Other languages German (de) Other versions DE2846202B2 (en DE2846202C3 (en … 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.. How does it work? Fig. as shown here, or any voltage more negative than +V. That collector current is determined by the 100k resistor current - it's the same - the current mirror does what it says on the tin and mirrors (or replicates) the current through the 100k. Here, an output (in some cases the only output) of the NPN mirror is used Re: PNP Current Mirror « Reply #1 on: May 05, 2014, 03:03:49 pm » Legion, The way you currently have your illustrations on your drawing for the I's.. this would be Hole Flow mode, not electron flow in a device. You can use a single transistor (the PNP one) but the transistor's base current slightly alters the ratio. be built with PNP transistors, and the general behavior, advantages, and IREF and Icopy1 can vary in large magnitude due to IS mismatch. 0000106860 00000 n IREF and Icopy1 can vary in large magnitude due to IS mismatch. control circuit of some kind, while the output mirrors are involved with Dealing with charge stores and coupling capacitors • Linear amplifiers Thread starter krlngc; Start date Nov 29, 2015; Search Forums; New Posts; Thread Starter. This is basic circuit. When we use both NPN and PNP transistors, we can use the same reference Current mirrors Current mirrors are important blocks in electronics. Popularly known as BJT, is a solid-state current controlled device. 0000017607 00000 n 0000004955 00000 n There is a 100:1 ratio of currents in the 3 PNPs in the mirror, and emitter areas need to be more proportional to the current. the mirror currents are always the same, regardless of any changes in +V2. Current mirrors consist of two branches that are parallel to each other and create two approximately equal currents. In the given current mirror, I o = 5 REF . PNP Mirror I I= V CC−0.7 R REF Current source model Q1 = Q2: Small signal model: i x= v eb1 r g m v eb1= 1 g m v eb1 i x= g m g m v eb1= 1 g m v eb1= v eb1 r e I Q1 Q2 v eb ix B1 C1 E1 B2 E2 C2 Current through r π and g m v eb1: re1 E1 E2 B1 C1 B2 C2 V CC=V EB1 IR REF r = g m r e= r 1 recall Also, as shown to the right, 0000011944 00000 n At first glance, the current mirror circuit shown to the right would seem to be backwards. 6.5 Current mirror OpAmp Another popular OpAmp when driving only on-chip capacitive loads is the current-mirror OpAmp. 2 illustrates a preferred embodiment of this invention. PNP Current mirror . This is by no means necessary; as shown to the left, we can easily use PNP transistors to build current mirrors. CH 9 Cascode Stages and Current Mirrors 44 Generation of IREF for PNP Current Mirror. Every mirror configuration that can be built with NPN transistors can also krlngc. Here, we are calculating the DC voltages (bias voltages) at every node of our circuit. %PDF-1.3 %���� By using proper current mirrors with high output impedance, good gain can be achieved. ZDS1009 Current mirror datasheet Keywords: Zetex - ZDS1009 Current mirror datasheet Battery chargers DC motor control Out-rush current sensing In-rush current sensing Wide operating voltage range Excellent temperature tracking characteristics Simplifies circuit implementation Only four connections required Created Date: 12/1/2006 2:31:01 PM version of the Wilson current mirror is limited to a single output, The first is the obvious fact that the applied voltage Reversing the circuit to obtain the true Wilson current mirror Only, there is something wrong in this connection because we can't change the input current in the left leg (by varying the resistor or the voltage). The output resistance of the current source (mirror) is used as active load in place of large-values collector resistance which cannot be fabricated conveniently on a chip. In the final section, we saw some examples of how current mirrors are incorporated into analog integrated circuits. The two aspects of the Wilson current mirror []. balanced voltages, and in such circuits the PNP collector circuits are A differential amplifier as in claim 6 where said active transistors are N-type field effect transistors. as the ground point is common to all circuits and the supply voltages are PNP current mirror is used as a current source load to an NPN amplifier stage. 0000017583 00000 n disadvantages of each configuration will be the same. Work-out what that will be on a 12 V PSU given also that there is about 0.6V lost in the base-emitter region. Circuit for pnp current mirror using simple device with dot-model statement shown Figure 1 shows a schematic for a pnp current mirror. 0000007067 00000 n An important feature of the current mirror is a relatively high output resistance which helps to … we assume VA→∞. 2. cause some very strange behavior. In next videos, we will cover Cascode current mirror, Wilson current mirror etc. {R�(�#��s�?.3�A �~ϙ8��lf2�(��K��h�h�$@��v]$B+�#;���q�8���q�N�[�~u���T�@�Rl��y��[����!$H Current mirrors consist of two branches that are parallel to each other and create two approximately equal currents. The output resistance of the current source (mirror) is used as active load in place of large-values collector resistance which cannot be fabricated conveniently on a chip. group have used NPN transistors. A current mirror is a circuit designed to copy a current through one active device by controlling the current in another active device of a circuit, keeping the output current constant regardless of loading. Weve seen already how maintaining a constant base current through an active transistor results in the regulation of collector current, according to the β ratio. current gain is necessarily more limited. Figure 2. Seminars; Webinars; Local Channel Partner. PMOS Current Mirror: • NMOS current source sinks current to ground • PMOS current source sources current from positive supply. The purpose of the mirror is to emulate an ideal current source, that is, to provide the same DC current through the output node regardless of the voltage applied, DC or transient. I E/ 1 vsig. both high enough for the purpose, all mirrors will work. Supporter; Posts: 609; Country: If you fail the first time, keep trying! 0000012577 00000 n 1 shows the basic npn current mirror. NPN transistors are made vertically, so the width of the base region can The Widlar circuit may be used with bipolar transistors, MOS transistors, and even vacuum tubes. Matched version of BCV62. 3. v sig is the signal source. Putting multiple references in multiple output lines would For its analysis, we assume identical transistors and neglect the Early effect, i.e. Note that at the Q2 side, more current mirrors needs to be used to provide current KI D2 =KI D1. In this, the current is flowing through one device can be copied into another device but in inverting form. One important factor when using multiple outputs from a current mirror: 0000005505 00000 n current mirror mirror circuit pnp current pnp circuit Prior art date 1977-10-31 Legal status (The legal status is an assumption and is not a legal conclusion. Current Mirror NPN current mirror with current source NPN current mirror with resistor PNP current mirror with resistor data. There are no extra calculations involving gate current, as there are with base current in bipolar junction transistors (BJTs). PNP Current Mirrors The Basic Current Mirror with PNP Transistors All of the current mirror circuits presented in previous pages in this group have used NPN transistors. use, but it does mean that their lower current gain must be accounted for, All pages on www.play-hookey.com copyright © 1996, 2000-2015 by. Technical Article Learn Analog Circuits: Types and Applications of Current Mirrors April 03, 2019 by Dr. Sergio Franco The current mirror is an important analog building block that finds application in such diverse areas as DC biasing and current-mode signal processing. ��N�N J���$aDّ�0!? Sep 13, 2017 Schematic Diagram. PNP The Current Mirror is a widely popular technique for monolithic IC design. *� 3. PNP BJT current mirror Small signal model Design example and simulation Comparison of CMRR with resistive load design. 0000009034 00000 n The current mirror sets I E (I C). The input current to the mirror is labeled IREF. The current mirror circuit gains its name because it copies or mirrors the current flowing in one active device in another, keeping the output current constant regardless of loading. 3. v sig is the signal source. These currents are used to load other stages in circuits and they are designed in such a way so that current is constant and independent of loading. The second factor to be considered is that in an IC, while it is always The device offers a current clamp to limit current through the APD and a current mir-ror output that produces a signal proportional (5:1) to the APD current. 3. These current mirrors can be made with NPN or PNP transistors. As a test, remove the load resistors R2,R3 and Cap C1 in the simulation, then short the Q1 collector to ground. Current source biasing Transistors as current sources Current mirror current sources and sinks • The mid-band concept. 7. some of the complex configurations cannot be used. The NPN current mirror, in its most basic form, is, in effect, an inverting current buffer in the sense that it changes current sources of any impedance into current sinks of high impedance. we assume VA →∞. In the first place, by doing it this way, we can have a circuit where 0000007501 00000 n 0000001778 00000 n The purpose of the mirror is to emulate an ideal current source, that is, to provide the same DC current through the output node regardless of the voltage applied, DC or transient. 2. either or both mirrors can have multiple outputs. And R E is the emitter resistor. Dr. Vincent Chang (張文清) Output Current I 3 I REF I 5 3I REF NPN Current mirrors I 4 2I REF. ouput circuit. By forming T2 with n transistors connected in parallel, the output current will be n times the input current, as shown in Figure 2a. circuit for both, as shown to the left. CH 9 Cascode Stages and Current Mirrors 44 Generation of IREF for PNP Current Mirror. commonly referenced to -V rather than to ground. idea to include the extra transistor to provide base current compensation In this technique, the circuit is designed in such a way that it copies the current through one active device to another active device with current control feature. Current mirror as differential amplifier. Download PSpice and try it for free! *Q�U����u�yt�P�=�QT��#R���Š�+ۗA���ĸ�@G�b�ń���zO���j؏~_ ESE319 Introduction to Microelectronics 2008 Kenneth R. Laker (based on P. V. Lopresti 2006) update 29Sep08 KRL 16 Bias Setting 1. because the diode-connected reference transistor in the mirror is in the This is why these circuits are called current mirrors. Input … ���,&T�ߙE�q���z�\�ߪ+⑳��*�2s�u3�n�;�Z��h�=3���~t�5}��Z3�` ��}���S�2J�}��ҟ,P٤>���/��36�1K��Iz���S �zZ�iu6�[V�-r:j��srEhF�7�&��|�k�y��ۛ>��9�J���g�Y��5nE��o�B��~������b}����A�WM:��3�kPZ��v��Z�"f^�km���sx��P��'ɨ4��M���-7�,&�Wy�����7oz��]�̩������'�[.��3��?�����6jq�0���g��ʫ{�}��:�:+N��Z��[�ڠ��-��e�� S��oT� ���1|]?C��7�O�Ϫ����rqF�wL���ZjM��'������k�+ �Z]�p�)�ۻGb �y[o ]�$+�jS��g:e���nm��=u�/�e�����:�q,�J�Q��ڞ_��%�z��7̃�l�ސ噦������Z�x����"��Ǿ)Ȅ%݋OZ�{I�R�EY�^}���6�Kl,5\iʭ�$�Q�,�b^���=|~d��� Download Free Trial. 0000013316 00000 n Joined Dec 9, 2013 11. PNP Current Mirror.jpg (36.73 kB, 409x500 - viewed 2750 times.) Multiple PNP current sources; IC3 and IC4 are matched to IC1 (the control tran- sistor) but IC2 is reduced by RE2.The Q2 – RE2 combination is a Widlar cur- rent source. 0000003155 00000 n 13 Bad MOS Current Mirror Example This is not a current mirror since the relationship between VX and IREF is not clearly defined. collectors are referenced to a more negative voltage. How does it work? The circuit consists of an input diffamp and four Wilson current mirrors. 0000003974 00000 n A current mirror is a circuit designed to copy a current through one active device by controlling the current in another active device of a circuit, keeping the output current constant regardless of loading. Matched version of BCV62. For the analysis, we assume β→∞and VA→∞for each bjt so that the output current from each mirror is equal to the input current. … The output impedance of a Widlar current mirror is approximately, where: r o = V AF /I C V AF is the Early voltage. scheme.png. Relevant source code lines: OP print all * Output current over constant input current (with 1V load): should be 1 for best match. in current mirrors. 8. Thank you . This makes the saturation current IS and current gain β independent of the collector- base voltage VCB. Circuit for pnp current mirror using simple device with dot-model statement shown. This ensures that This is a true current mirror: feed a current (i 1) into the first transistor (usually by driving it via a resistor ... use ICs, here is a current source (or a voltage to current converter) using an IC. outputs is to change the areas of the transistor emitters. Current mirrors are basic building blocks of analog design. possible to manufacture both NPN and PNP transistors on the same die, it In PNP transistors, the majority charge (current) carriers are holes and the electrons are the minority charge carriers. Another way to link NPN and PNP current mirrors is shown to the right. 14 Example: Current Scaling Similar to their bipolar counterpart, MOS current mirrors can also scale IREF up or down (I1 = 0.2mA, I2 = 0.5mA). polarities, there are several possible reasons for doing it this way Build a mirror using PNP transistors and use the output impedance of the simple mirror to determine the Early voltage for the PNP transistor. A differential amplifier as in claim 2 where said one current mirror means is a PNP transistor and the reverse polarity transistors are NPN transistors. There is a large collector current variation with changes in collector voltage (due to the early effect), moreover the effect is more pronounced for the lateral PNP current mirror than it was for the Widlar current mirror, mainly: We may consider the behavior of Wilson current mirror from two aspects. The circuit is shown in Fig. 0000004723 00000 n instead. Either can be higher than the other; as long 2. Current Mirror with Multiple Outputs PNP Current mirrors NPN Current mirrors S E v V i C I S e BE T I A. Dr. Vincent Chang (張文清) Output Current I 3 I REF PNP Current mirrors. transistors"), which means the base region must be wider, so the 0000011688 00000 n Concept of using a current mirror circuit to allow subtraction of collector currents Oct 31, 1977 - GTE Sylvania Incorporated. R b serves no purpose except to provide a path for the base current. For example, any Thus, let us learn more about all this in the upcoming sections. if multiple outputs are used. It also operates at a relatively high signal frequency. I E/ 1 vsig All this is best done on an integrated circuit, but if you could find matched transistors or use enough emitter degeneration resistance you could come up with something that works. Lecture20-Current Mirrors 10 MOS Current Mirrors Changing the Mirror Ratio Mirror ratio can be changed by modifying W/L ratios of the two transistors forming the mirror. Dr. Vincent Chang (張文清) Output Current I 3 I REF I 5 3I REF PNP Current mirrors. The DS3920 precision current mirror is designed for ava-lanche photodiode (APD) and PIN photodiode biasing and monitoring applications. polarity must be reversed. I build a demonstration current mirror circuit using 2n3906 transistors. There are only two differences in using PNP rather than NPN transistors This is by no means necessary; as shown 6.012 Spring 2007 Lecture 25 9 3. Attachments. Logged jlmoon. 0000003179 00000 n 0000014733 00000 n Current Mirror NPN current mirror with current source NPN current mirror with resistor PNP current mirror with resistor I B =. Thus, the simplest bias condition for design of the mirror sets the applied voltage VA to equal the base voltage VB. For its analysis, we assume identical transistors and neglect the Early e ffect, i.e. PNP/PNP matched double transistor in a SOT143B small Surface-Mounted Device (SMD) plastic package. Also, it can be seen that all internal nodes have low impedance except the output node. In addition, the bandwidth of frequency response of the PNP current mirror is very narrow because of the loss of signal transmission through parasitic capacitance and excessive transit time. It makes sense that the bases would share a common voltage with Q1's collector, but the text states "You 'program' the mirror by sinking a current from Q1's collector." Current mirrors are basic building blocks of analog design. This is why these circuits are called current mirrors. 0000107148 00000 n emitter area will transmit more current for a given value of Bipolar Junction Transistor. 0000010446 00000 n unnecessary, and no different from using a common reference for both g m = I C /V T is the transconductance. Fig. 0000003814 00000 n 0000011712 00000 n A diode is also provided to limit the voltage at the current mirror output. 17.9 KB … It does not "regulate" current. In some cases, +V1 is heavily regulated and filtered. Resource Library; PSpice Forum; Service Bureaus; Channel Partners; Events . CH 9 Cascode Stages and Current Mirrors 45 Current Mirror with Discrete Devices Let QREF and Q1 be discrete NPN devices. The current being mirrored can be a constant current, or it can be a varying signal dependent upon the … Ø� ����ǝp.���<2�����`�\C1�0��. In next videos, we will cover Cascode current mirror, Wilson current mirror etc. Build a mirror using PNP transistors and use the output impedance of the simple mirror to determine the Early voltage for the PNP transistor. The current mirror sets I E (I C). the same for npn and pnp; the same for n-MOS and p-MOS; all parameters depend on bias; maintaining a stable bias is critical • Biasing transistors. Common Emitter Amplifier - Current Source Biasing 1. R b serves no purpose except to provide a path for the base current. 0000001982 00000 n They are widely used in several applications and chips, the operational amplifier being one of them. AIC-1.3.2: Current Mirrors -- Lateral PNP Current Mirror. All of the current mirror circuits presented in previous pages in this The current being "copied" can be, and sometimes is, a varying signal current. A preferred embodiment operates at high accuracy over a wide range of output currents. 0000001838 00000 n I use a mutimeter to take current measurements of the circuit. Generally, it's a good 0000001718 00000 n be closely controlled to enable high values of current gain. T1 and T2 are PNP transistors and form together a current mirror.