EP1213636A2 - Current mirror circuit - Google Patents

Current mirror circuit Download PDF

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Publication number
EP1213636A2
EP1213636A2 EP01127473A EP01127473A EP1213636A2 EP 1213636 A2 EP1213636 A2 EP 1213636A2 EP 01127473 A EP01127473 A EP 01127473A EP 01127473 A EP01127473 A EP 01127473A EP 1213636 A2 EP1213636 A2 EP 1213636A2
Authority
EP
European Patent Office
Prior art keywords
current
mirror circuit
output
branch
current mirror
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP01127473A
Other languages
German (de)
French (fr)
Other versions
EP1213636A3 (en
Inventor
Johannes Gerber
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Texas Instruments Deutschland GmbH
Original Assignee
Texas Instruments Deutschland GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Texas Instruments Deutschland GmbH filed Critical Texas Instruments Deutschland GmbH
Publication of EP1213636A2 publication Critical patent/EP1213636A2/en
Publication of EP1213636A3 publication Critical patent/EP1213636A3/en
Withdrawn legal-status Critical Current

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    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05F—SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
    • G05F3/00—Non-retroactive systems for regulating electric variables by using an uncontrolled element, or an uncontrolled combination of elements, such element or such combination having self-regulating properties
    • G05F3/02—Regulating voltage or current
    • G05F3/08—Regulating voltage or current wherein the variable is dc
    • G05F3/10—Regulating voltage or current wherein the variable is dc using uncontrolled devices with non-linear characteristics
    • G05F3/16—Regulating voltage or current wherein the variable is dc using uncontrolled devices with non-linear characteristics being semiconductor devices
    • G05F3/20—Regulating voltage or current wherein the variable is dc using uncontrolled devices with non-linear characteristics being semiconductor devices using diode- transistor combinations
    • G05F3/26—Current mirrors
    • G05F3/267—Current mirrors using both bipolar and field-effect technology

Definitions

  • the invention relates to a current mirror circuit for producing an output current flowing in an output branch corresponding to a reference current flowing in an input branch located between a supply voltage terminal and ground, including a first bipolar transistor in the input branch through the collector/emitter circuit of which the reference current furnished by a current source connected to the collector flows and a second bipolar transistor in the output branch through the collector/emitter circuit of which the output current flows, the bases of the two transistors being connected to each other.
  • Current mirror circuits are used to generate a current in an output branch corresponding as precisely as possible to a current flowing in an input branch. It is also possible to generate the current in such a circuit in the output branch so that it is available in a precise ratio to the current in the input branch.
  • two bipolar transistors 10, 12 are provided, the first of which is located in the input branch whilst the second is located in the output branch.
  • the reference current I r flowing in the input branch for mirroring in the output branch as the current I a is generated by a current source 14.
  • the bases of the two transistors 10 and 12 are connected to each other and the base current I b required by these transistors is furnished via the drain/source circuit of a MOS field-effect transistor 16 the gate of which is connected to the collector of the transistor 10. Since the gate of the MOS field-effect transistor 16 absorbs no current it is the reference current I r generated by the current source 14 that flows through the collector/emitter circuit of the transistor 10. This current then flows due to the known current mirror effect also through the collector/emitter circuit of the transistor 12 so that the desired effect is achieved, namely that in the output branch of the circuit a current I a flows corresponding to the reference current I r .
  • the supply voltage V DD amounts only to 1.8 V as may very well be the case in practical applications then a voltage of not more than 0.4 V is available for operation of the current source 14 which is not sufficient to configure the current source 14 with simple means to reliably furnish the desired reference current I r .
  • the circuit as shown in Fig. 2 is only suitable for operation with higher supply voltages.
  • the invention is based on the object of configuring a current mirror circuit of the aforementioned kind so that it is able, despite low operating voltages, to mirror the reference current flowing in the input branch with high accuracy in the output branch.
  • a further current mirror circuit having an input branch located between the supply voltage terminal and ground and an output branch located between the supply voltage terminal and the connected bases of the two bipolar transistors for generating a base current for these transistors, a current source controlled by the collector voltage of the first bipolar transistor being located in the input branch of this further current mirror circuit, the output current of this current source being mirrored in the output branch of this further current mirror circuit.
  • the base current required for the bipolar transistors is produced by a further current mirror circuit capable of producing this base current in its output branch without requiring current to be branched from the reference current I r . Due to making use of this further current mirror circuit and its current source located in the input branch between the supply voltage terminal and ground the unavoidable drop in voltage is greatly reduced so that the voltage remaining for operating the current source furnishing the reference current I r in the input branch becomes corresponding larger. The current mirror circuit is thus able to mirror the reference current I r in its output branch with high accuracy even when the supply voltage is low.
  • Fig. 1 there is illustrated the current mirror circuit containing as its basic components the two bipolar transistors 10 and 12 as well as the current source 14 furnishing the reference current I r .
  • the output current I a to be generated flows through a load resistor R.
  • the circuit as shown in Fig. 1 contains a further current mirror circuit consisting of two p-channel MOS field-effect transistors 16 and 18 as well as an n-channel MOS field-effect transistor 20 acting as the current source.
  • the gates of the p-channel MOS field-effect transistors 16 and 18 are connected to each other whilst their sources receive the supply voltage V DD .
  • the drain of the p-channel MOS field-effect transistor 16 is connected to the gates of these two MOS transistors.
  • the drain of the p-channel MOS field-effect transistor 16 is connected to the drain of the n-channel MOS field-effect transistor 20 whose source is directly grounded.
  • a voltage occurs at the point A which corresponds to the threshold voltage V th of the n-channel MOS field-effect transistor 20.
  • V DD the supply voltage
  • V th the threshold voltage of the n-channel MOS field-effect transistor 20.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Nonlinear Science (AREA)
  • Electromagnetism (AREA)
  • General Physics & Mathematics (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Automation & Control Theory (AREA)
  • Control Of Electrical Variables (AREA)

Abstract

A current mirror circuit serves to produce an output current flowing in an output branch corresponding to a reference current flowing in an input branch located between a supply voltage terminal and ground. Located in the input branch is a first bipolar transistor (10) through the collector/emitter circuit of which the reference current furnished by a current source (14) connected to the collector flows. Through the collector/emitter circuit of a second bipolar transistor (12) located in the output branch the output current flows. The bases of the two transistors (10, 12) are connected to each other. A further current mirror circuit (16, 18, 20) is provided having an input branch located between the supply voltage terminal and ground and an output branch located between the supply voltage terminal and the connected bases of the two bipolar transistors (10, 12) for generating a base current (Ib) for these transistors. A current source (20) controlled by the collector voltage of the first bipolar transistor (10) is located in the input branch of this further current mirror circuit (16, 18, 20), the output current (2Ib) of said current source (20) being mirrored in the output branch of said further current mirror circuit (16, 18, 20).

Description

  • The invention relates to a current mirror circuit for producing an output current flowing in an output branch corresponding to a reference current flowing in an input branch located between a supply voltage terminal and ground, including a first bipolar transistor in the input branch through the collector/emitter circuit of which the reference current furnished by a current source connected to the collector flows and a second bipolar transistor in the output branch through the collector/emitter circuit of which the output current flows, the bases of the two transistors being connected to each other.
  • Current mirror circuits are used to generate a current in an output branch corresponding as precisely as possible to a current flowing in an input branch. It is also possible to generate the current in such a circuit in the output branch so that it is available in a precise ratio to the current in the input branch. In a known circuit of this kind, as shown in Fig. 2, two bipolar transistors 10, 12 are provided, the first of which is located in the input branch whilst the second is located in the output branch. The reference current Ir flowing in the input branch for mirroring in the output branch as the current Ia is generated by a current source 14. As evident, the bases of the two transistors 10 and 12 are connected to each other and the base current Ib required by these transistors is furnished via the drain/source circuit of a MOS field-effect transistor 16 the gate of which is connected to the collector of the transistor 10. Since the gate of the MOS field-effect transistor 16 absorbs no current it is the reference current Ir generated by the current source 14 that flows through the collector/emitter circuit of the transistor 10. This current then flows due to the known current mirror effect also through the collector/emitter circuit of the transistor 12 so that the desired effect is achieved, namely that in the output branch of the circuit a current Ia flows corresponding to the reference current Ir.
  • Although this known circuit as shown in Fig. 2 satisfies the cited condition very precisely it has drawbacks when only a small supply voltage VDD is available as is often the case in modern battery-powered electronic instruments. As evident a voltage materializes at point A of the circuit corresponding to the sum of the base/emitter voltage of the bipolar transistor 10 and the threshold voltage Vth of the MOS field-effect transistor 16. These two voltages amount to roughly 0.7 V so that at point A a voltage of at least 1.4 V occurs. When, however, the supply voltage VDD amounts only to 1.8 V as may very well be the case in practical applications then a voltage of not more than 0.4 V is available for operation of the current source 14 which is not sufficient to configure the current source 14 with simple means to reliably furnish the desired reference current Ir. Thus, the circuit as shown in Fig. 2 is only suitable for operation with higher supply voltages.
  • The invention is based on the object of configuring a current mirror circuit of the aforementioned kind so that it is able, despite low operating voltages, to mirror the reference current flowing in the input branch with high accuracy in the output branch.
  • This object is achieved in a current mirror circuit of the aforementioned kind by a further current mirror circuit having an input branch located between the supply voltage terminal and ground and an output branch located between the supply voltage terminal and the connected bases of the two bipolar transistors for generating a base current for these transistors, a current source controlled by the collector voltage of the first bipolar transistor being located in the input branch of this further current mirror circuit, the output current of this current source being mirrored in the output branch of this further current mirror circuit.
  • In the current mirror circuit in accordance with the invention the base current required for the bipolar transistors is produced by a further current mirror circuit capable of producing this base current in its output branch without requiring current to be branched from the reference current Ir. Due to making use of this further current mirror circuit and its current source located in the input branch between the supply voltage terminal and ground the unavoidable drop in voltage is greatly reduced so that the voltage remaining for operating the current source furnishing the reference current Ir in the input branch becomes corresponding larger. The current mirror circuit is thus able to mirror the reference current Ir in its output branch with high accuracy even when the supply voltage is low.
  • The invention will now be detailled by way of example with reference to the drawing in which:
    • Fig. 1
    is a circuit diagram of a current mirror circuit in accordance with the invention and
    Fig. 2
    is a circuit diagram of a prior art current mirror circuit.
  • Referring now to Fig. 1 there is illustrated the current mirror circuit containing as its basic components the two bipolar transistors 10 and 12 as well as the current source 14 furnishing the reference current Ir. The output current Ia to be generated flows through a load resistor R.
  • The circuit as shown in Fig. 1 contains a further current mirror circuit consisting of two p-channel MOS field- effect transistors 16 and 18 as well as an n-channel MOS field-effect transistor 20 acting as the current source. The gates of the p-channel MOS field- effect transistors 16 and 18 are connected to each other whilst their sources receive the supply voltage VDD. The drain of the p-channel MOS field-effect transistor 16 is connected to the gates of these two MOS transistors. Furthermore, the drain of the p-channel MOS field-effect transistor 16 is connected to the drain of the n-channel MOS field-effect transistor 20 whose source is directly grounded.
  • As evident from Fig. 1 a voltage occurs at the point A which corresponds to the threshold voltage Vth of the n-channel MOS field-effect transistor 20. This means that for the same supply voltage VDD for operating the current source 14 a voltage is available which as compared to that of the current mirror circuit as shown in Fig. 2 is higher by the base/emitter voltage Vbe. For a supply voltage VDD of 1.8 V and a threshold voltage Vth of 0.7 V a voltage of 1.1 V is thus available at the circuit point A. It is with this voltage that the current source 14 can be operated by simple ways and means. The wanted object, namely to mirror the reference current Ir flowing in the input branch precisely in the output branch is thus achieved by very simple circuitry.

Claims (2)

  1. A current mirror circuit for producing an output current flowing in an output branch corresponding to a reference current flowing in an input branch located between a supply voltage terminal and ground, including a first bipolar transistor in the input branch through the collector/emitter circuit of which the reference current furnished by a current source connected to the collector flows and a second bipolar transistor in the output branch through the collector/emitter circuit of which the output current flows, the bases of the two transistors being connected to each other, characterized by a further current mirror circuit (16, 18, 20) having an input branch located between the supply voltage terminal and ground and an output branch located between the supply voltage terminal and the connected bases of the two bipolar transistors (10, 12) for generating a base current (Ib) for these transistors, a current source (20) controlled by the collector voltage of the first bipolar transistor (10) being located in the input branch of this further current mirror circuit (16, 18, 20), the output current (2Ib) of said current source (20) being mirrored in the output branch of said further current mirror circuit (16, 18, 20).
  2. The current mirror circuit as set forth in claim 1, characterized in that said controlled current source is an n-channel MOS field-effect transistor (20) whose source is grounded, that said further current mirror circuit contains two p-channel MOS field-effect transistors (16, 18) whose gates are connected to each other, the drain of the one p-channel MOS field-effect transistor (16) being connected to the drain of said n-channel MOS field-effect transistor (20) and its gate, and the drain of the other p-channel MOS field-effect transistor (18) being connected to the bases of said two bipolar transistors bipolar transistor (10, 12) whilst the sources of said p-channel MOS field-effect transistors (16, 18) are connected to the supply voltage terminal.
EP01127473A 2000-12-07 2001-11-28 Current mirror circuit Withdrawn EP1213636A3 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE10060842 2000-12-07
DE2000160842 DE10060842C2 (en) 2000-12-07 2000-12-07 Current mirror circuit

Publications (2)

Publication Number Publication Date
EP1213636A2 true EP1213636A2 (en) 2002-06-12
EP1213636A3 EP1213636A3 (en) 2004-08-04

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EP01127473A Withdrawn EP1213636A3 (en) 2000-12-07 2001-11-28 Current mirror circuit

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DE (1) DE10060842C2 (en)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1387234A1 (en) * 2002-07-29 2004-02-04 Motorola Energy Systems Inc. Current copy circuit arrangement
US7170337B2 (en) 2004-04-20 2007-01-30 Sige Semiconductor (U.S.), Corp. Low voltage wide ratio current mirror
WO2017030849A2 (en) * 2015-08-14 2017-02-23 Qualcomm Incorporated Fully differential charge pump with switched-capacitor common-mode feedback

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102005019157A1 (en) 2005-04-25 2006-10-26 Robert Bosch Gmbh Metal oxide semiconductor field effect transistor arrangement for use in integrated circuit, has source and gate connections of transistors that are connected with each other and that contact connections of chip, respectively
CN108491021A (en) * 2018-04-04 2018-09-04 浙江天狼半导体有限责任公司 A kind of current mirroring circuit that tool temperature is anti-

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3024422A1 (en) * 1980-06-28 1982-01-21 Philips Patentverwaltung Gmbh, 2000 Hamburg Monolithic integrated image current circuit - has five transistors to produce image ratio of up to 0.999
EP0443239A1 (en) * 1990-02-20 1991-08-28 Precision Monolithics Inc. Current mirror with base current compensation
JPH06138967A (en) * 1992-10-26 1994-05-20 Matsushita Electric Ind Co Ltd Current mirror circuit
US5675243A (en) * 1995-05-31 1997-10-07 Motorola, Inc. Voltage source device for low-voltage operation

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3024422A1 (en) * 1980-06-28 1982-01-21 Philips Patentverwaltung Gmbh, 2000 Hamburg Monolithic integrated image current circuit - has five transistors to produce image ratio of up to 0.999
EP0443239A1 (en) * 1990-02-20 1991-08-28 Precision Monolithics Inc. Current mirror with base current compensation
JPH06138967A (en) * 1992-10-26 1994-05-20 Matsushita Electric Ind Co Ltd Current mirror circuit
US5675243A (en) * 1995-05-31 1997-10-07 Motorola, Inc. Voltage source device for low-voltage operation

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 0184, no. 41 (P-1788), 17 August 1994 (1994-08-17) & JP 6 138967 A (MATSUSHITA ELECTRIC IND CO LTD), 20 May 1994 (1994-05-20) *

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1387234A1 (en) * 2002-07-29 2004-02-04 Motorola Energy Systems Inc. Current copy circuit arrangement
US7170337B2 (en) 2004-04-20 2007-01-30 Sige Semiconductor (U.S.), Corp. Low voltage wide ratio current mirror
WO2017030849A2 (en) * 2015-08-14 2017-02-23 Qualcomm Incorporated Fully differential charge pump with switched-capacitor common-mode feedback
WO2017030849A3 (en) * 2015-08-14 2017-03-30 Qualcomm Incorporated Fully differential charge pump with switched-capacitor common-mode feedback

Also Published As

Publication number Publication date
EP1213636A3 (en) 2004-08-04
DE10060842C2 (en) 2002-11-28
DE10060842A1 (en) 2002-07-11

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