CA1093164A - Biasing and scaling circuit for transducers - Google Patents
Biasing and scaling circuit for transducersInfo
- Publication number
- CA1093164A CA1093164A CA303,905A CA303905A CA1093164A CA 1093164 A CA1093164 A CA 1093164A CA 303905 A CA303905 A CA 303905A CA 1093164 A CA1093164 A CA 1093164A
- Authority
- CA
- Canada
- Prior art keywords
- operational amplifier
- circuit
- field effect
- biasing
- scaling
- 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.)
- Expired
Links
Classifications
-
- 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
- G01D3/06—Indicating or recording apparatus with provision for the special purposes referred to in the subgroups with provision for operation by a null method
-
- 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
- G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
- G01D5/12—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P15/00—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration
- G01P15/02—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses
- G01P15/08—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values
Abstract
ABSTRACT OF THE DISCLOSURE
In order to provide a substantially error free biasing and scaling circuit for transducer signals an operational amplifier and a field effect transistor are used in combination with a DC voltage source to bias and scale the transducer signal.
In order to provide a substantially error free biasing and scaling circuit for transducer signals an operational amplifier and a field effect transistor are used in combination with a DC voltage source to bias and scale the transducer signal.
Description
3~
BACKGROUND OF THE INVENTION
The invention relates to the field of signal biasing and scaling circuits and more particularly scaling and biasing circuits for use with small signal transducers.
Since transducers, such as accelerometers, used in telemetry systems generally have small signal outputs that are of both a positive and negative polarity, it is quite often necessary to convert those outputs to signals of a single polarity due to the fact that many of the telemetry systems require that the input signals be of a single polarity and of a 1~ limited voltage range such as zero to five volts DC. Also due to the fact that telemetry systems often require signals of great accuracy, it is highly desirable that any biasing or scaling circuits introduce an absolute minimum of error into the signals. In addition, many of the prior art biasing and scaling circuits used with telemetry systems require a negative source of DC voltage which in many cases is not available within the telemetry system itself.
In other prior art systems utilizing positive voltage sources in combination with transistor elements, quite often errors are introduced into the signal output due to temperature effects on the transistors or result from the base currents in the transistors themselves. In addition the current voltage characteristics of the transistor elements tended to vary with temperature thereby adding an additonal source of error.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide a scaling and biasing circuit utilizing an operational amplifier and field effect transistor in combination with a positive DC voltage source.
It is additional object of the invention to provide a biasing and scaling circuit for use with transducer signals including: a positive DC
voltage source wherein the voltage source is connected by means of a zener diode to one terminal of an operational amplifier, the other terminal of the operational amplif;er connected by means of a b;as res;stor to the " ~ , . .. . . .
~ 9~
voltage source and to the transducer by means of a scaling resistor, a field effect trans;stor having its gate connected to the output of the operational amplifier and source and drain connected between the positive terminal of the operational amplifier and a load resistor.
BRIEF DESCRIPTION_OF THE DRAWINGS
Fig. 1 is a schematic drawing of a prior art bias and scaling circuit; and Fig. 2 is a schematic drawing of a bias and scaling circuit.
DETAILED DESCRIPTION OF THE INVENTION
Illustrated in Fig. 1 of the drawings is a typical example of a prior art biasing and scaling circuit. A 28-volt DC source 10 is connected by means of a zener diode 12 to the base of a PNP transistor 14. A bias resistor RB is connected between the voltage source 10 and the emitter of transistor 14 and a scaling resistor Rs is also connected between the emitter of transistor 14 and a transducer signal source 16. The collector of transistor 14 is connected to a load resistor RL across which a biased and scaled output signal Eo is generated. In normal operation the PNP
transistor 14 serves as a feedback element to adjust the bias current IB
flowing through Rb in response to the transducer 16 input signdl Es so that the correct bias and scaling currents are applied to the load resistor RL-The above described arrangement in Fig. 1, unfortunately, often results in certain errors in the output signal Eo~ For example, since there is an appreciable base current Ib, not all of the current being applied to the emitter of the transistor 14 will flow through the load resistor RL. In addition, the voltage at the emitter of transistor 14 can vary as a function of the base to emitter voltage of transistor 14 which in turn may vary with temperature thereby introducing significant errors into the output signal Eo~
In order to overcome these difficulties, the biasing and scaling circuit of Fig. 2 was developed. As in the case of the circuit of Fig. 1 a 28-volt DC voltage source 10 is utilized to provide a positive source of .. :-; ., , ... ~ . .
~ 3 ~
bias current and voltage. However, as shown in F;g. 2, the anode of zener diode 12 is connected to a negative terminal of an operation amplifier 18.
A positive terminal of operational ampliFier 18 is connected through current summing junction 20 and biasing resistor RB to the voltage source 10. Similarly, transducer signal source 16 is connected through scaling resistor Rs to the current summing junction 20. Connected to the output of the operational amplifier 18 on line 22 is the gate of a N-channel field effect transistor 24. The source and drain terminals of the field effect transistor 24 are then connected between the summing junction 20 and load ln resistor Rl.
In normal operation the operational amplifier 18 will cooperate with field effect tarnsistor 24 to provide a negative feedback loop in response to signal inputs Es from transducer 16 so that the appropriate biasing current IB and scaling current Is will flow through load resistor RL
to provide an accurate single polarity signal Eo that represents Es~
For example if the signal voltage Es should increase, the operational amplifier 18 will generate a positive output cn:~ ne 22 thereby permitting increased current to flow through field effect transistor 24. The bias current IB will increase so as to maintain the voltage drop across the biasing resistor R~ equal the voltage drop Vz across the zener diode 12. Thus, the operational amplifier 18 in combination with field effect transistor 24 will act as a negative servo loop maintaining the correct value of the biasing current IB. The operation of the circuit of Fig. 2 may be represented by the equation:
RL RL
E = -- ( ES ~ ) + R V z ( 1 ) In the above equation (1) the quantity Er is the voltage at the negative terminal of the operational amplifier 18. In the circuit of Fig. 2 the scale factor may be represented by RL/Rs and the biasing factor by RL~Rb . Vz. It should also be noted at this point that a P-channel field effect transistor could be used in place of the N-channel field effect transistor 24 if the polarity of the inputs of operational amplifier 18 were reversed.
. , .3,~ a~
The scaling and biasing circuit shown in Fig. 2 has a very significant advantage over the circuit shown in Fig. 1 in that due to the fact that field effect transistors are very high impedance circuit elements there will be no appreciable current flowing in line 22. This will result in a negligible diversion of current from the load resistor RL thereby enhancing the accuracy of the biasing and scaling circuit.
BACKGROUND OF THE INVENTION
The invention relates to the field of signal biasing and scaling circuits and more particularly scaling and biasing circuits for use with small signal transducers.
Since transducers, such as accelerometers, used in telemetry systems generally have small signal outputs that are of both a positive and negative polarity, it is quite often necessary to convert those outputs to signals of a single polarity due to the fact that many of the telemetry systems require that the input signals be of a single polarity and of a 1~ limited voltage range such as zero to five volts DC. Also due to the fact that telemetry systems often require signals of great accuracy, it is highly desirable that any biasing or scaling circuits introduce an absolute minimum of error into the signals. In addition, many of the prior art biasing and scaling circuits used with telemetry systems require a negative source of DC voltage which in many cases is not available within the telemetry system itself.
In other prior art systems utilizing positive voltage sources in combination with transistor elements, quite often errors are introduced into the signal output due to temperature effects on the transistors or result from the base currents in the transistors themselves. In addition the current voltage characteristics of the transistor elements tended to vary with temperature thereby adding an additonal source of error.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide a scaling and biasing circuit utilizing an operational amplifier and field effect transistor in combination with a positive DC voltage source.
It is additional object of the invention to provide a biasing and scaling circuit for use with transducer signals including: a positive DC
voltage source wherein the voltage source is connected by means of a zener diode to one terminal of an operational amplifier, the other terminal of the operational amplif;er connected by means of a b;as res;stor to the " ~ , . .. . . .
~ 9~
voltage source and to the transducer by means of a scaling resistor, a field effect trans;stor having its gate connected to the output of the operational amplifier and source and drain connected between the positive terminal of the operational amplifier and a load resistor.
BRIEF DESCRIPTION_OF THE DRAWINGS
Fig. 1 is a schematic drawing of a prior art bias and scaling circuit; and Fig. 2 is a schematic drawing of a bias and scaling circuit.
DETAILED DESCRIPTION OF THE INVENTION
Illustrated in Fig. 1 of the drawings is a typical example of a prior art biasing and scaling circuit. A 28-volt DC source 10 is connected by means of a zener diode 12 to the base of a PNP transistor 14. A bias resistor RB is connected between the voltage source 10 and the emitter of transistor 14 and a scaling resistor Rs is also connected between the emitter of transistor 14 and a transducer signal source 16. The collector of transistor 14 is connected to a load resistor RL across which a biased and scaled output signal Eo is generated. In normal operation the PNP
transistor 14 serves as a feedback element to adjust the bias current IB
flowing through Rb in response to the transducer 16 input signdl Es so that the correct bias and scaling currents are applied to the load resistor RL-The above described arrangement in Fig. 1, unfortunately, often results in certain errors in the output signal Eo~ For example, since there is an appreciable base current Ib, not all of the current being applied to the emitter of the transistor 14 will flow through the load resistor RL. In addition, the voltage at the emitter of transistor 14 can vary as a function of the base to emitter voltage of transistor 14 which in turn may vary with temperature thereby introducing significant errors into the output signal Eo~
In order to overcome these difficulties, the biasing and scaling circuit of Fig. 2 was developed. As in the case of the circuit of Fig. 1 a 28-volt DC voltage source 10 is utilized to provide a positive source of .. :-; ., , ... ~ . .
~ 3 ~
bias current and voltage. However, as shown in F;g. 2, the anode of zener diode 12 is connected to a negative terminal of an operation amplifier 18.
A positive terminal of operational ampliFier 18 is connected through current summing junction 20 and biasing resistor RB to the voltage source 10. Similarly, transducer signal source 16 is connected through scaling resistor Rs to the current summing junction 20. Connected to the output of the operational amplifier 18 on line 22 is the gate of a N-channel field effect transistor 24. The source and drain terminals of the field effect transistor 24 are then connected between the summing junction 20 and load ln resistor Rl.
In normal operation the operational amplifier 18 will cooperate with field effect tarnsistor 24 to provide a negative feedback loop in response to signal inputs Es from transducer 16 so that the appropriate biasing current IB and scaling current Is will flow through load resistor RL
to provide an accurate single polarity signal Eo that represents Es~
For example if the signal voltage Es should increase, the operational amplifier 18 will generate a positive output cn:~ ne 22 thereby permitting increased current to flow through field effect transistor 24. The bias current IB will increase so as to maintain the voltage drop across the biasing resistor R~ equal the voltage drop Vz across the zener diode 12. Thus, the operational amplifier 18 in combination with field effect transistor 24 will act as a negative servo loop maintaining the correct value of the biasing current IB. The operation of the circuit of Fig. 2 may be represented by the equation:
RL RL
E = -- ( ES ~ ) + R V z ( 1 ) In the above equation (1) the quantity Er is the voltage at the negative terminal of the operational amplifier 18. In the circuit of Fig. 2 the scale factor may be represented by RL/Rs and the biasing factor by RL~Rb . Vz. It should also be noted at this point that a P-channel field effect transistor could be used in place of the N-channel field effect transistor 24 if the polarity of the inputs of operational amplifier 18 were reversed.
. , .3,~ a~
The scaling and biasing circuit shown in Fig. 2 has a very significant advantage over the circuit shown in Fig. 1 in that due to the fact that field effect transistors are very high impedance circuit elements there will be no appreciable current flowing in line 22. This will result in a negligible diversion of current from the load resistor RL thereby enhancing the accuracy of the biasing and scaling circuit.
Claims (5)
1. A bias and scaling circuit for use with a source of signals from a transducer or the like comprising:
a voltage source;
an operational amplifier having a first and a second input terminal and an output terminal, a diode connected between said voltage source and said first operational amplifier input terminal;
a current summing junction connected to said second operational amplifier input;
a bias resistor connected between said voltage source and said current summing junction;
a scaling resistor connected between the signal source and said current summing junction;
a field effect transistor having a gate terminal connected to said operational amplifier output terminal and an input terminal connected to said current summing junction; and a load resistor connected to an output terminal of said field effect transistor.
a voltage source;
an operational amplifier having a first and a second input terminal and an output terminal, a diode connected between said voltage source and said first operational amplifier input terminal;
a current summing junction connected to said second operational amplifier input;
a bias resistor connected between said voltage source and said current summing junction;
a scaling resistor connected between the signal source and said current summing junction;
a field effect transistor having a gate terminal connected to said operational amplifier output terminal and an input terminal connected to said current summing junction; and a load resistor connected to an output terminal of said field effect transistor.
2. The circuit of Claim 1 wherein said voltage source is a source of positive direct current.
3. The circuit of Claim 1 wherein said diode is a zener diode.
4. The circuit of Claim 2 wherein:
said first operation amplifier input terminal is a negative terminal; and said second operational amplifier input terminal is a positive terminal.
said first operation amplifier input terminal is a negative terminal; and said second operational amplifier input terminal is a positive terminal.
5. The circuit of Claim 4 wherein said field effect transistor is an N-channel field effect transistor.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US05/804,419 US4125789A (en) | 1977-06-07 | 1977-06-07 | Biasing and scaling circuit for transducers |
| US804,419 | 1977-06-07 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1093164A true CA1093164A (en) | 1981-01-06 |
Family
ID=25188932
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA303,905A Expired CA1093164A (en) | 1977-06-07 | 1978-05-23 | Biasing and scaling circuit for transducers |
Country Status (9)
| Country | Link |
|---|---|
| US (1) | US4125789A (en) |
| JP (1) | JPS544159A (en) |
| CA (1) | CA1093164A (en) |
| DE (1) | DE2821938C3 (en) |
| FR (1) | FR2394208A1 (en) |
| GB (1) | GB1576668A (en) |
| IT (1) | IT1105358B (en) |
| SE (1) | SE431702B (en) |
| SU (1) | SU854282A3 (en) |
Families Citing this family (26)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS53105334A (en) * | 1977-02-25 | 1978-09-13 | Nippon Soken | Nonnlinear calculating circuit |
| US4257064A (en) * | 1980-02-19 | 1981-03-17 | Hughes Aircraft Company | Wideband linear video contrast control |
| US4598251A (en) * | 1982-06-16 | 1986-07-01 | Rosemount Inc. | Frequency to current converter circuit |
| EP0112380B1 (en) * | 1982-06-16 | 1991-02-27 | Rosemount Inc. | Frequency to current converter circuit |
| DE3312027A1 (en) * | 1983-04-02 | 1984-11-15 | Pierburg Gmbh & Co Kg, 4040 Neuss | DEVICE FOR ZERO-POINT ADJUSTMENT OF SIGNAL SOURCES, IN PARTICULAR SENSOR ARRANGEMENTS |
| US4558239A (en) * | 1983-08-17 | 1985-12-10 | At&T Bell Laboratories | High impedance amplifier for an IC chip |
| US4593213A (en) * | 1984-05-25 | 1986-06-03 | United Technologies Corporation | Current-limited MOSFET switch |
| JPH0410149Y2 (en) * | 1984-10-18 | 1992-03-12 | ||
| JPH0191179U (en) * | 1987-12-09 | 1989-06-15 | ||
| US5012140A (en) * | 1990-03-19 | 1991-04-30 | Tektronix, Inc. | Logarithmic amplifier with gain control |
| JP2867756B2 (en) * | 1991-08-30 | 1999-03-10 | 日本電気株式会社 | Power consumption control device |
| FI99171C (en) * | 1991-09-12 | 1997-10-10 | Nokia Mobile Phones Ltd | Connection for RSSI signal output voltage scaling |
| US5438288A (en) * | 1993-05-28 | 1995-08-01 | National Semiconductor Corporation | High differential output impedance setter |
| US9950282B2 (en) * | 2012-03-15 | 2018-04-24 | Flodesign Sonics, Inc. | Electronic configuration and control for acoustic standing wave generation |
| US10704021B2 (en) | 2012-03-15 | 2020-07-07 | Flodesign Sonics, Inc. | Acoustic perfusion devices |
| US9458450B2 (en) | 2012-03-15 | 2016-10-04 | Flodesign Sonics, Inc. | Acoustophoretic separation technology using multi-dimensional standing waves |
| JP6286925B2 (en) * | 2013-08-19 | 2018-03-07 | ヤマハ株式会社 | Audio signal processing device |
| US9725710B2 (en) | 2014-01-08 | 2017-08-08 | Flodesign Sonics, Inc. | Acoustophoresis device with dual acoustophoretic chamber |
| US11021699B2 (en) | 2015-04-29 | 2021-06-01 | FioDesign Sonics, Inc. | Separation using angled acoustic waves |
| US11377651B2 (en) | 2016-10-19 | 2022-07-05 | Flodesign Sonics, Inc. | Cell therapy processes utilizing acoustophoresis |
| US11708572B2 (en) | 2015-04-29 | 2023-07-25 | Flodesign Sonics, Inc. | Acoustic cell separation techniques and processes |
| US11474085B2 (en) | 2015-07-28 | 2022-10-18 | Flodesign Sonics, Inc. | Expanded bed affinity selection |
| US11459540B2 (en) | 2015-07-28 | 2022-10-04 | Flodesign Sonics, Inc. | Expanded bed affinity selection |
| US11085035B2 (en) | 2016-05-03 | 2021-08-10 | Flodesign Sonics, Inc. | Therapeutic cell washing, concentration, and separation utilizing acoustophoresis |
| US11214789B2 (en) | 2016-05-03 | 2022-01-04 | Flodesign Sonics, Inc. | Concentration and washing of particles with acoustics |
| US10785574B2 (en) | 2017-12-14 | 2020-09-22 | Flodesign Sonics, Inc. | Acoustic transducer driver and controller |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3504267A (en) * | 1968-02-20 | 1970-03-31 | Bendix Corp | Voltage to frequency converter |
| US3839648A (en) * | 1972-02-28 | 1974-10-01 | Tektronix Inc | Programmable function generation |
| DE2209787C2 (en) * | 1972-03-01 | 1974-03-14 | Auergesellschaft Gmbh, 1000 Berlin | Circuit arrangement for suppressing common-mode signals in measuring arrangements caused by changes in common-mode voltage |
| US3870906A (en) * | 1973-06-21 | 1975-03-11 | Us Navy | Ramp/hold circuit |
| US3839647A (en) * | 1973-11-08 | 1974-10-01 | Litton Systems Inc | Transistor linearizer circuit |
-
1977
- 1977-06-07 US US05/804,419 patent/US4125789A/en not_active Expired - Lifetime
-
1978
- 1978-05-19 DE DE2821938A patent/DE2821938C3/en not_active Expired
- 1978-05-23 CA CA303,905A patent/CA1093164A/en not_active Expired
- 1978-05-26 GB GB23502/78A patent/GB1576668A/en not_active Expired
- 1978-06-02 SE SE7806489A patent/SE431702B/en not_active IP Right Cessation
- 1978-06-05 IT IT49701/78A patent/IT1105358B/en active
- 1978-06-06 JP JP6735978A patent/JPS544159A/en active Granted
- 1978-06-06 FR FR787816888A patent/FR2394208A1/en active Granted
- 1978-06-07 SU SU782628152A patent/SU854282A3/en active
Also Published As
| Publication number | Publication date |
|---|---|
| SE7806489L (en) | 1978-12-05 |
| FR2394208A1 (en) | 1979-01-05 |
| JPS544159A (en) | 1979-01-12 |
| DE2821938A1 (en) | 1978-12-14 |
| GB1576668A (en) | 1980-10-15 |
| JPS6144360B2 (en) | 1986-10-02 |
| IT7849701A0 (en) | 1978-06-05 |
| US4125789A (en) | 1978-11-14 |
| DE2821938C3 (en) | 1980-12-11 |
| SE431702B (en) | 1984-02-20 |
| SU854282A3 (en) | 1981-08-07 |
| FR2394208B1 (en) | 1982-07-30 |
| IT1105358B (en) | 1985-10-28 |
| DE2821938B2 (en) | 1980-03-27 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CA1093164A (en) | Biasing and scaling circuit for transducers | |
| US4448549A (en) | Temperature sensing device | |
| US4475077A (en) | Current control circuit | |
| JPH0570326B2 (en) | ||
| US4134030A (en) | Hall-effect integrated circuit switch | |
| US4647839A (en) | High precision voltage-to-current converter, particularly for low supply voltages | |
| US4362956A (en) | Absolute value circuit | |
| US3474258A (en) | Solid state relays | |
| JPH0656394B2 (en) | Signal selection circuit | |
| US5585746A (en) | Current sensing circuit | |
| US4001602A (en) | Electronic analog divider | |
| US3555402A (en) | Constant current temperature stabilized signal converter circuit | |
| GB1297867A (en) | ||
| KR20000075637A (en) | Current-limit circuit | |
| US3544882A (en) | Electric current range converting amplifier | |
| US3531656A (en) | Precision rectifier circuit | |
| US4792704A (en) | Scaled voltage level translator circuit | |
| EP0157447B1 (en) | Differential amplifier | |
| US5485123A (en) | Circuit configuration for adjusting the quadrature-axis current component of a push-pull output stage | |
| US4004161A (en) | Rectifying circuits | |
| US3417319A (en) | Constant current apparatus | |
| US4370608A (en) | Integrable conversion circuit for converting input voltage to output current or voltage | |
| US3588728A (en) | Impedance bridge transducer circuits | |
| US3602832A (en) | Low zero-offset transducer apparatus | |
| EP0110720B1 (en) | Current mirror circuit |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |