GB2202624A - Optimum biasing system for electronic devices - Google Patents
Optimum biasing system for electronic devices Download PDFInfo
- Publication number
- GB2202624A GB2202624A GB08706793A GB8706793A GB2202624A GB 2202624 A GB2202624 A GB 2202624A GB 08706793 A GB08706793 A GB 08706793A GB 8706793 A GB8706793 A GB 8706793A GB 2202624 A GB2202624 A GB 2202624A
- Authority
- GB
- United Kingdom
- Prior art keywords
- control system
- bias
- operational amplifier
- pass filter
- signal
- 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- Withdrawn
Links
- 230000035945 sensitivity Effects 0.000 claims abstract description 10
- 238000001514 detection method Methods 0.000 claims abstract 2
- 239000003990 capacitor Substances 0.000 claims description 3
- 230000003750 conditioning effect Effects 0.000 claims description 3
- 230000008878 coupling Effects 0.000 claims description 2
- 238000010168 coupling process Methods 0.000 claims description 2
- 238000005859 coupling reaction Methods 0.000 claims description 2
- 238000001914 filtration Methods 0.000 claims 2
- 230000001681 protective effect Effects 0.000 claims 1
- 230000036039 immunity Effects 0.000 abstract 2
- 238000010586 diagram Methods 0.000 description 4
- 238000000034 method Methods 0.000 description 4
- 230000006641 stabilisation Effects 0.000 description 3
- 230000000694 effects Effects 0.000 description 2
- 230000003321 amplification Effects 0.000 description 1
- 238000010348 incorporation Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000003199 nucleic acid amplification method Methods 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J1/00—Photometry, e.g. photographic exposure meter
- G01J1/42—Photometry, e.g. photographic exposure meter using electric radiation detectors
- G01J1/4204—Photometry, e.g. photographic exposure meter using electric radiation detectors with determination of ambient light
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D3/00—Indicating or recording apparatus with provision for the special purposes referred to in the subgroups
- G01D3/02—Indicating or recording apparatus with provision for the special purposes referred to in the subgroups with provision for altering or correcting the law of variation
- G01D3/021—Indicating or recording apparatus with provision for the special purposes referred to in the subgroups with provision for altering or correcting the law of variation using purely analogue techniques
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J1/00—Photometry, e.g. photographic exposure meter
- G01J1/42—Photometry, e.g. photographic exposure meter using electric radiation detectors
- G01J1/44—Electric circuits
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J1/00—Photometry, e.g. photographic exposure meter
- G01J1/42—Photometry, e.g. photographic exposure meter using electric radiation detectors
- G01J1/44—Electric circuits
- G01J2001/444—Compensating; Calibrating, e.g. dark current, temperature drift, noise reduction or baseline correction; Adjusting
Abstract
A biasing system is described which provides essentially total immunity against slow background fluctuations, coupled with excellent detection sensitivity for fast signals. Its principle is a control loop, based on an operational amplifier 15, which senses the output voltage of the device 10 and adjusts the bias applied to it via a network 16, so that it remains at a constant level, determined by the reference bias 14. The bias generating network 16 also acts as dynamic load and thus high stage gain can be achieved, yielding excellent sensitivity and S/N ratio. The control is made effective at low frequencies only, by including a low pass filter 13. Thus, high frequency signals are unaffected. The principle is illustrated with a photodiode circuit which provides immunity against extreme variations in ambient lighting conditions. <IMAGE>
Description
OPTIMUM BIRSING SYSTEM FOR ELECTRONIC DEVICES
This invention relates to an improved technique for controlline the operatine point of electronic devices, so that their output is made insensitive to SLOWLY varying backeround fluctuations, while excellent sensitivity can be achieved to FRST sienals.
Various techniques are in existence for biasing electronic devices e.g. transistors, Photodetectors etc., so that their often strone dependence on backeround Parameters, such as temperature and light, is minimised. In general, these techniques suffer from several disadvantages viz.
i) they require making a compromise between operating point stability and signal sensitivity, since the circuit configurations used to reduce their dependence on background fluctuations also reduce the device sensitivity against the signals themselves. ii) they yield limited dynamic range circuits and introduce non-linearities in the system response even in regions well away from the saturation points. This makes circuit design Problematic, since it necessitates either a Priori knowledge of the dynamic range limits or the incorporation of some form of external adjustment, which is usually undesirable, due to its subjective nature and the incumbent loss of equipment
simplicity. iii) some require considerable circuit complexity e.g. second or third order temperature compensation circuits.
According to the present invention, the system consists of an electronic device to be stabilised and a control system which maintains the operating Point of the device to a constant, Pre-determined value.
A specific embodiment of the invention will now be described by way of example for the stabilisation of a photodetector against background light fluctuations. It should, however, be emphasised that the applicability of the technique is very general and encompasses the stabilisation of essentially ANY device against external influences. Examples are : the stabilisation of transistors, diodes and other semiconductors against temperature fluctuations and of transducers against background fluctuations of the Parameter that they are supposed to measure (e.g. magnetic sensor stabilised against the earth's magnetic field) etc.
The core of a basic, general system is described with reference to the block diagram shown in Figure 1.
The Electronic Device 10 is followed by an (optional) Signal
Conditioning Circuit 11, which produces a suitable Output
Voltage 12 Proportional to the parameter of interest (e.g.
light level). This Output Voltage is fed through a Low Pass
Filter 13 to one input of an Operational Amplifier 15 which forms the bias control loop.
This input of the Operational Amplifier must obviously be chosen with due regard to signal inversions around the various intervening circuits so that it results in overall
NEGRTIVE feedback, otherwise the system will be unstable.
Some form of frequency compensation (not shown in this diagram) may be necessary, in order to achieve stability.
The other input of the Operational Amplifier is connected to the Reference Bias block 14 which sets up a voltage corresponding to the required operating point conditions.
The Operational Amplifier is followed by the Bias
Generating Network 16, which produces the correct biasing conditions for the Device. This network 16 also serves as a high impedance dynamic load for the Device, so that very high values of voltage gain can be obtained which result in excellent sensitivity and improved Signal Noise performance since high gain is placed EARLY in the amplification chain of the system. This point will become clearer in the
Photodiode circuit outlined below. An important component of the system is the Low Pass Filter. This allows essentially complete insensitivity against SLOW variations of the parameter under measurement (assuming that an
Operational Amplifier of sufficiently high gain has been used,, due to the effect of the negative feedback which forces the output voltage to be equal to the reference bias.This is because the Low Pase Filter shapes the frequency response of the loop gain so that it is very high at low frequencies but drops to zero at high frequencies.
Thus, the useful signal is not affected by the negative feedback, if care is taken to ensure that the low frequency limit (3db point) of the passband is well ABOVE the corner frequency of the Low Pass Filter (by say a decade). and full signal sensitivity is maintained.
A specific example to illustrate the application of the above general principles to a photodiode circuit is shown in Figure 2. In this case the Electronic Device 10 is the
Photodiode D2. There is no need for Signal Conditioning
Circuit 11, since the photodiode produces a voltage
Proportional to the light level which can be fed directly to the Low Pass Filter 13 formed by the resistor-capacitor combination C1,R1. The Reference Bias 14 is simply a dc voltage level generated externally (its generation is trivial and is not shown in this sketchy circuit diagram).
IC1 is the Operational Amplifier 15 with the correct input
Polarity for this particular application (TR1 causes a signal inversion).
The transistor TR1 forms a voltage controlled current source and is, therefore, the Bias Generating Network 16.
This current source has a very high dynamic impedance (of the oder of mega ohms) and therefore a very high voltage gain can be achieved at the output 12. Care must be taken not to lower this high impedance by loading the collector of TR1. Thus R1 must be very high, as must be the input impedance of the following stage (connected at point 12).
Ideally, this stage should be an impedance converting buffer, such as an emmiter or source follower, in oder to minimise loading effects. The photodiode 10 can be operated either with zero voltage bias, resulting in the highest possible sensitivity but relatively slow response (due to the depletion layer capacitance) or with reverse bias, which yields the fastest possible response, since it minimises this capacitance. In order to avoid the possibility of applying forward bias to the photodiode (even transiently),
which could damage it from exceessive power dissipation, a protection circuit has been incorporated. This consists of the diode D1 and associated resistor at the base of TR1.
This part of the circuit does not have a counterpart in the general diagram shown in Figure 1, since it is specific to this Particular application and it is not unique (different or additional means of protection may be incorporated at various parts of the circuit). Similarly, the coupling capacitor C2 does not have a counterpart in Figure 1. It forms effectively a high pass filter (together with the input impedance of the following circuitry), so that the dc bias voltage of the photodiode is blocked out and does not cause saturation of the following stages. It can also serve the purpose of increasing the steepness of the slope of the overall system frequency response from 6db/octave to 12 db/octave in combination with the Low Pass Filter 13, by matching the 3 db points of the two filters.
Claims (5)
1. A control system for biasing an electronic device so that slow background fluctuations are suppressed, while excellent sensitivity is attained with high frequency modulation of the parameter constituting the useful signal.
The background parameter may be the same as the signal parameter (e.g. the detection of modulated light in the
Presence of ambient light) but could be different (e.g. the reduction of thermal drift in a device measuring electrical signals) The system includes, in combination, an operational amplifier which compares the output voltage of the device after filtering through a low pass filter with a reference bias and a bias generating network which is driven by the operational amplifier and supplies the device with suitable biasing conditions.
2. A control system according to claim 1, wherein a signal conditioning circuit is interposed between the electronic device and the low pass filter, in order to produce a convenient output voltage.
3. A control system according to claim 1 or claim 2 wherein the bias generating network 16 acts as a high impedance dynamic load for the device 10, so that a very high value of voltage gain can be obtained, giving excellent sensitivity and improved signal to noise ratio.
4. A control system according to any of the Precedine claims applied to the biasing of a photodetector as described in figure 2, wherein one or more of the following additional features have been incorporated: a) protective means to safeguard the device against overload and b) a coupling capacitor to avoid saturation of the following stages and to improve the filtering action at low frequencies ( increase the slope steepness of the frequency response ).
5. A control system for a photodetector, substantially as described with reference to Figures 1 and 2 of the accompanying drawings.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB08706793A GB2202624A (en) | 1987-03-23 | 1987-03-23 | Optimum biasing system for electronic devices |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB08706793A GB2202624A (en) | 1987-03-23 | 1987-03-23 | Optimum biasing system for electronic devices |
Publications (2)
Publication Number | Publication Date |
---|---|
GB8706793D0 GB8706793D0 (en) | 1987-04-29 |
GB2202624A true GB2202624A (en) | 1988-09-28 |
Family
ID=10614419
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
GB08706793A Withdrawn GB2202624A (en) | 1987-03-23 | 1987-03-23 | Optimum biasing system for electronic devices |
Country Status (1)
Country | Link |
---|---|
GB (1) | GB2202624A (en) |
Cited By (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB2367945A (en) * | 2000-08-16 | 2002-04-17 | Secr Defence | Photodetector Circuit |
DE102005044679A1 (en) * | 2005-09-19 | 2007-03-22 | Vishay Semiconductor Gmbh | Circuit arrangement for supplying a photodiode with a bias voltage |
US7271376B2 (en) | 2002-07-11 | 2007-09-18 | Qinetiq Limited | Avalanche photodiode with reduced sidewall defects |
US7515822B2 (en) | 2006-05-12 | 2009-04-07 | Microsoft Corporation | Imaging systems' direct illumination level adjusting method and system involves adjusting operation of image sensor of imaging system based on detected level of ambient illumination |
CN108204859A (en) * | 2018-02-27 | 2018-06-26 | 京东方科技集团股份有限公司 | Photoelectric detective circuit and photoelectric detection system |
CN109506776A (en) * | 2017-09-15 | 2019-03-22 | 阿自倍尔株式会社 | Photoelectric sensor |
Citations (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB1103954A (en) * | 1964-05-28 | 1968-02-21 | Peyer Siegfried | Photoelectric amplifier circuit |
GB1124576A (en) * | 1966-01-06 | 1968-08-21 | Reliance Electric & Eng Co | Hall effect transducer systems |
GB1285885A (en) * | 1968-11-07 | 1972-08-16 | Atomic Energy Authority Uk | Improvements in or relating to nephelometers |
GB1449289A (en) * | 1972-12-21 | 1976-09-15 | Schlumberger Ltd | Apparatus for stabilizing the gain of radiation detectors |
GB1458594A (en) * | 1973-08-24 | 1976-12-15 | Thaelmann Schwermaschbau Veb | Optical diameter-measuring apparatus |
EP0070590A1 (en) * | 1981-07-21 | 1983-01-26 | Océ-Nederland B.V. | Light-sensitive detection circuit |
GB2136626A (en) * | 1983-03-16 | 1984-09-19 | Philips Nv | Optical end-of-tape detection device |
-
1987
- 1987-03-23 GB GB08706793A patent/GB2202624A/en not_active Withdrawn
Patent Citations (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB1103954A (en) * | 1964-05-28 | 1968-02-21 | Peyer Siegfried | Photoelectric amplifier circuit |
GB1124576A (en) * | 1966-01-06 | 1968-08-21 | Reliance Electric & Eng Co | Hall effect transducer systems |
GB1285885A (en) * | 1968-11-07 | 1972-08-16 | Atomic Energy Authority Uk | Improvements in or relating to nephelometers |
GB1449289A (en) * | 1972-12-21 | 1976-09-15 | Schlumberger Ltd | Apparatus for stabilizing the gain of radiation detectors |
GB1458594A (en) * | 1973-08-24 | 1976-12-15 | Thaelmann Schwermaschbau Veb | Optical diameter-measuring apparatus |
EP0070590A1 (en) * | 1981-07-21 | 1983-01-26 | Océ-Nederland B.V. | Light-sensitive detection circuit |
GB2136626A (en) * | 1983-03-16 | 1984-09-19 | Philips Nv | Optical end-of-tape detection device |
Cited By (10)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB2367945A (en) * | 2000-08-16 | 2002-04-17 | Secr Defence | Photodetector Circuit |
GB2367945B (en) * | 2000-08-16 | 2004-10-20 | Secr Defence | Photodetector circuit |
US6858912B2 (en) | 2000-08-16 | 2005-02-22 | Qinetiq Limited | Photodetector circuit |
US7271376B2 (en) | 2002-07-11 | 2007-09-18 | Qinetiq Limited | Avalanche photodiode with reduced sidewall defects |
DE102005044679A1 (en) * | 2005-09-19 | 2007-03-22 | Vishay Semiconductor Gmbh | Circuit arrangement for supplying a photodiode with a bias voltage |
US7515822B2 (en) | 2006-05-12 | 2009-04-07 | Microsoft Corporation | Imaging systems' direct illumination level adjusting method and system involves adjusting operation of image sensor of imaging system based on detected level of ambient illumination |
CN109506776A (en) * | 2017-09-15 | 2019-03-22 | 阿自倍尔株式会社 | Photoelectric sensor |
CN109506776B (en) * | 2017-09-15 | 2021-04-23 | 阿自倍尔株式会社 | Photoelectric sensor |
CN108204859A (en) * | 2018-02-27 | 2018-06-26 | 京东方科技集团股份有限公司 | Photoelectric detective circuit and photoelectric detection system |
CN108204859B (en) * | 2018-02-27 | 2020-05-01 | 京东方科技集团股份有限公司 | Photoelectric detection circuit and photoelectric detection device |
Also Published As
Publication number | Publication date |
---|---|
GB8706793D0 (en) | 1987-04-29 |
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Legal Events
Date | Code | Title | Description |
---|---|---|---|
WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |