GB2042840A - RC-bridge Oscillator - Google Patents
RC-bridge Oscillator Download PDFInfo
- Publication number
- GB2042840A GB2042840A GB7938690A GB7938690A GB2042840A GB 2042840 A GB2042840 A GB 2042840A GB 7938690 A GB7938690 A GB 7938690A GB 7938690 A GB7938690 A GB 7938690A GB 2042840 A GB2042840 A GB 2042840A
- Authority
- GB
- United Kingdom
- Prior art keywords
- frequency
- operational amplifier
- voltage divider
- series
- resistor
- 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.)
- Granted
Links
Classifications
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03B—GENERATION OF OSCILLATIONS, DIRECTLY OR BY FREQUENCY-CHANGING, BY CIRCUITS EMPLOYING ACTIVE ELEMENTS WHICH OPERATE IN A NON-SWITCHING MANNER; GENERATION OF NOISE BY SUCH CIRCUITS
- H03B5/00—Generation of oscillations using amplifier with regenerative feedback from output to input
- H03B5/20—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element comprising resistance and either capacitance or inductance, e.g. phase-shift oscillator
- H03B5/26—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element comprising resistance and either capacitance or inductance, e.g. phase-shift oscillator frequency-determining element being part of bridge circuit in closed ring around which signal is transmitted; frequency-determining element being connected via a bridge circuit to such a closed ring, e.g. Wien-Bridge oscillator, parallel-T oscillator
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03B—GENERATION OF OSCILLATIONS, DIRECTLY OR BY FREQUENCY-CHANGING, BY CIRCUITS EMPLOYING ACTIVE ELEMENTS WHICH OPERATE IN A NON-SWITCHING MANNER; GENERATION OF NOISE BY SUCH CIRCUITS
- H03B5/00—Generation of oscillations using amplifier with regenerative feedback from output to input
- H03B5/02—Details
- H03B5/04—Modifications of generator to compensate for variations in physical values, e.g. power supply, load, temperature
Landscapes
- Oscillators With Electromechanical Resonators (AREA)
- Inductance-Capacitance Distribution Constants And Capacitance-Resistance Oscillators (AREA)
- Amplifiers (AREA)
Abstract
An operational amplifier giving 90 DEG phase-shift at the oscillating frequency has frequency independent feed-back provided by a voltage divider, incorporating series and parallel-connected resistors R1-R5, limiting diodes D1, D2 and a thermistor T, and frequency determining positive feedback 1, 2. The thermistor T compensates the temperature changes of the limiting diodes, while the series or parallel connected resistors are adjusted for balancing this temperature compensation in order to ensure very slight voltage level changes of the sense tending to stabilise the frequency. Moreover, the RC-value of the positive, feed-back branch, and the division ratio of the frequency- independent branch, are determined in dependence on the basic amplification of the operational amplifier, the first break-point frequency, and the intended operating frequency. Buffer stages or amplifiers can be inserted between the oscillator and the load. If a square-wave signal is required on the output, a comparator is used instead of the buffer stage. <IMAGE>
Description
SPECIFICATION
High Frequency-stability Wien-Robinson
Bridge Oscillator
The subject of the invention is an RC-oscillator of Wien-Robinson bridge arrangement, containing an operational amplifier and having a wide frequency overlapping, low nonlinear distortion, good short and long term frequency-stability as well as good frequency-supply voltage and frequency-temperature stability.
There are many application fields where relatively high frequency stability ( 10-4) oscillators have to be used. For satisfying like requirements high frequency stability quartzoscillators are commonly used. Applications of audio-frequency quartz-oscillators however, have numerous disadvantages. The frequency produced by the quartz-oscillator cannot be chosen at will since the designer should abide by the frequencies of obtainable quartz-crystals on the one hand, and moreover, the production and application of audio-frequency quartz-crystals is disadvantageous because of their large size, on the other. For this reason, the audio-frequency oscillators are sometimes replaced by highfrequency quartz-oscillators followed by frequency dividers, working out the necessary audio-frequencies.Another possible solution is the application of RC oscillators. The frequency and amplitude stability of the known RCoscillators as a function of variations of the temperature, supply voltage and load is several orders worse than that of quartz oscillators.
For increasing the stability of Wien-bridge RCoscillators according to Hungarian patent specification No. 162,974 there are several operational amplifiers inserted in the positive feed-back circuit. This solution, however is rather sophisticated and disproportionately expensive, but in spite of that its frequency-stability has only the order 10-3.
Other known Wien-Robinson bridge oscillators have only one operational amplifier, containing both a negative feed-back circuit and a positive feed-back branch. The positive feed-back circuit contains a selective resistor-capacitor term and the negative feed-back branch includes a circuit, dependant on voltage level. This voltage leveldependant circuit performs the desired limitation by means of diodes or thermistors in the known circuits. A negative feedback thermistor circuit of this kind has been described in the West German patent specification No. 1,196,722. This solution however, ensures only amplitude stability in a relatively narrow range, leaving the problem of frequency stabilisation unresolved.
There is no known solutions suitable for common stabilisation both the frequency and the amplitude in a wide temperature range.
The present invention proposes a simple, low cost resistance-capacitance oscillator characterised by high frequency and amplitude stability in a wide temperature range.
The idea, leading to the implementation of the invention, has been the realisation that considerable frequency and amplitude stability can be attained by using an operational amplifier, having 900 phase-shift at the oscillation frequency and by performing the feed-back independently of frequency by means of a voltage divider, containing limiting diodes, thermistor and some resistors, connected in series and in parallel with them.The thermistor compensates for the temperature dependence characteristics of the limiting diodes; while the series- and parallelconnected resistors enable the adjustment of temperature compensation such that the temperature changes should cause only very small voltage changes and only in the sense or direction tending to stabilise the frequency; furthermore, the RC value of the frequencydependent selective, positive feed-back branch and the division ratio of the frequencyindependent branch should be selected after taking into account the basic gain of the operational amplifier; and its first breakpoint frequency; and its temperature-dependence are adjusted or set so as to prevent the oscillation frequency from changing within the given temperature range.
The invention thus provides a high frequency stability Wien-Robinson bridge oscillator containing an operational amplifier of 900 phaseshift, ensuring frequency-dependent feed-back and amplitude dependent feed-back from its output.
The frequency-dependant feed-back branch is a voltage divider consisting of a series RC-term and a parallel RC-term. The division-point of the divider is connected with the non-inverting input of an operational amplifier. The amplitudedependant feed-back circuit is also a voltage divider having its division point connected to the inverting input of the operational amplifier.The very essence of the invention is that the product of multiplication of the resistance and capacitance of each of the RC-terms, included in the frequency-dependant feed-back branch should be equal to:
where
R-the value of resistance in the respective RO term
C-the value of the capacitance in the respective RC term fr7the frequency to be produced A0-basic gain of the operational amplifier f0-first break-point frequency of the response of the operational amplifier (Bode diagram).
One of the two terms of the voltage divider, forming the amplitude-dependant feed-back branch consists of a series-connected resistor, joining a pair of parallel connected diodes, connected in opposite senses to one another, and a resistor, connected in parallel with them. The other term of the voltage divider is built up of a resistor, connected in series with a thermistor and a series resistor, as well as of a resistor, connected in parallel to this series-connected resistor and thermistor. The division ratio of the voltage divider, forming the amplitude-dependant feed-back circuit, is determined by the formula:
The output of the oscillator may, in accordance with the invention be connected to a separating stage between the amplifier and the load.
An embodiment of the present invention will now be described with reference to the accompanying drawing.
As can be seen in this Figure, an operational amplifier E is fed-back from its output UOut to both its inputs, namely the selective circuit of the resistor R and capacitor C represents the positive feed-back circuit depending on frequency while the negative feedback circuit consists of diodes Dl, D2, resistors R1, R2, R3 R4, R5 and thermistor T. The selective feeding-back network is formed of a series RC-circuit 1 and a parallel
RC-term 2, representing a voltage divider. The non-inverting input of the operational amplifier E is attached to the division-point 3 of this voltage divider.The following formula is suitable for calculating the selective feed-back branch of the oscillator:
where:
R-the value of the resistor R in each term of the feed-back network;
C-the value of the capacitor C in each term of the feed-back network; fr-the frequency to be produced; A0-the basic gain of the operational amplifier; f0-first break-point frequency of the response of the operational amplifier (Bode diagram).
The basic gain Ao and the first break-point frequency f, can be set up relatively simply for the operational amplifier E. The way of setting up depends on the type of operational amplifier used, and on its catalogue data. It is important, however, that the basic gain Ao be set up at such a frequency f which is lower by some orders than the first break-point frequency f, and the possible second breakpoint frequency be higher by some orders than the frequency fr to be produced. The operational amplifier E has also an amplitudedependant feed-back circuit, connected with its inverting input.This feed-back circuit consists of series-connected resistors R1 and R2 and a pair of parallel-connected opposite sense diodes D1 and D2, connected in parallel also with the resistor R2, representing one of the terms of a voltage divider. The division point of the divider is connected to the inverting input of the operational amplifier E. The other term of the voltage divider includes series-connected resistors R4 and R5, a thermistor T with a series resistor R3 together connected in parallel with the resistor R.4. The grounding point of the two voltage dividers is a common point.The frequency-independent feeding-back branch behaves as a temperaturedependent and amplitude-dependent voltage divider when properly designed so that the calculation of the frequency-independent feedback branch can be done on the basis of the following correlation:
The division ratio is:
where: RT~the resistance of the thermistor at the mean temperature of the temperature range to be compensated;
-R1, R2, R3, R4, RS-values of the resistors in the feed-back branch; division rate of the frequency-independent feed-back branch.
The amplitude of the output signal of the oscillator can be adjusted by changing the ratio
R1/R2. The oscillator, performed according to the invention, is sensitive only slightly to the instability of the supply voltage. If during the operation of the amplifier the supply voltage is always within an apt supply voltage range, the amplifier will not limit the amplitude of the oscillating signal and the frequency of the oscillator will practically be independent of the supply voltage.
If even greater frequency stability ( 10-5) is required, then a stable common temperature should be ensured for all elements (resistors, capacitors, operational amplifier) of the oscillator.
This problem can be settled for example, by arranging the whole circuitry within a good heatinsulating capsule, filled with some relatively good heat-conducting material, or by building all parts and elements of the circuitry on a common aluminium mass, flanked by a cover of reliable heat-insulating material.
As was mentioned above, oscillators are also sensitive to changes of the loading impedance.
The oscillator can be protected from the effects of a changing load impedance by the well-known means of a separating stage, for instance a follower amplifier inserted between the oscillator and the loading circuit. If a square-wave signal is required as output signal of the oscillator, then a comparator is used instead of the separating stage.
According to the above description, the suggested circuit diagram of the invention is suitable for implementing RC-oscillators by relatively simple means. These oscillators offer 10-4 frequency stability, good amplitude, stability and accuracy within a relatively wide temperature range and long time period.
Claims (5)
1. A high frequency stability Wien-Robinson bridge oscillator, containing an operational amplifier having a frequency-dependant positive feedback as well as an amplitudedependant negative feedback loop from its output; the frequency-dependant feed-back loop consists of a voltage divider formed by a series RC-circuit element and a parallel RCcircuit element, the divisional point of the voltage divider being coupled to the non-inverting input of the operational amplifier; the amplitude-dependant feed-back loop is also a voltage divider the division-point of which is connected with the inverting input of the operational amplifier, characterised in that the operational amplifier has a 900 phase-shift at and adjacent the oscillation frequency, moreover, the product of multiplication of the resistances and capacitances in the frequency-dependant feed-back loop is given by:
where:
R-the resistance of the resistor;
C-the capacitance of the capacitor; fr-the frequency to be produced; AO--basic gain of the operational amplifier; f0-first break-point frequency of the operational amplifier response; while one element of the voltage divider representing the amplitude-dependant feed back loop consists of two series-connected resistors (R1 and R2) and two diodes (D1 and D2) of opposite polarity connected in parallel with one (R2) of the resistors; the other member or element of this voltage divider is formed of a) a thermistor (T) connected in series with a resistor (R5) and preferably also of b) a resistor (R3) connected in series to the thermistor (T) and c) of a resistor (R4) connected in parallel with the resistor (R3) and the thermistor (T); wherein the division ratio of this voltage divider of this amplitude-dependant feedback loop is determined by:
2. The embodiment of the oscillator, according to claim 1 wherein the oscillator output is connected to the load through a separating stage, advantageously a follower amplifier.
3. A high frequency-stability Wien-Robinson bridge oscillator comprising an operational amplifier having a 900 phase-shift at and adjacent the oscillation frequency, a frequency-dependant positive feed-back loop comprising a voltage divider formed by a series RC element and a parallel RC element, the division point of which is coupled to the non-inverting input of the amplifier and the product of the multiplication of the resistance and capacitance of each RC element of the voltage divider being given by:
where::
R is the value of the resistance in each RC element;
C is the value of the capacitance in each RC element; fr is the frequency to be produced; Ao is the basic gain of the operational amplifier; f, is the first break-point of the operational amplifier response and an amplitude-dependant negative feed back loop comprising a voltage divider the division point of which is connected to .the inverting input of the operational amplifier and the division ratio of which is given by:
4.An oscillator according to Claim 3 wherein one side of the amplitude dependant voltage divider comprises a pair of limiting diodes connected in parallel with one another but in opposite senses, a first resistor connected in series with the diodes and a second resistor connected in parallel with the diodes, and the other side of the voltage divider including a third resistor connected in series with a thermistor for compensating temperature changes of the limiting diodes, a fourth resistor connected in parallel with the series connected thermistor and third resistor, and a fourth resistor connected in series with the parallel combination of the thermistor and the third and fourth resistors, the arrangement being such that the division ratio of the voltage divider is given by: :
where R,, R2, R3, R4, R5 and RT are the resistors of the first to fifth resistors and the thermistor respectively.
5. A high frequency stability Wien-Robinson bridge oscillator substantially as shown in and as hereinbefore described with reference to the accompanying drawing.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| HUTE000918 HU178124B (en) | 1978-12-11 | 1978-12-11 | Wien-robinson bridge oscillator of high frequency stability |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB2042840A true GB2042840A (en) | 1980-09-24 |
| GB2042840B GB2042840B (en) | 1983-04-13 |
Family
ID=11002088
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB7938690A Expired GB2042840B (en) | 1978-12-11 | 1979-11-08 | Rc-bridge oscillator |
Country Status (6)
| Country | Link |
|---|---|
| CS (1) | CS221529B2 (en) |
| DD (1) | DD146728A5 (en) |
| DE (1) | DE2945999C2 (en) |
| GB (1) | GB2042840B (en) |
| HU (1) | HU178124B (en) |
| PL (1) | PL123572B1 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2017151290A1 (en) * | 2016-03-02 | 2017-09-08 | Qualcomm Incorporated | Systems and methods for compensating for variation in an amplitude-regulated oscillator |
| CN113037306A (en) * | 2019-12-25 | 2021-06-25 | 成都鼎桥通信技术有限公司 | Amplitude limiting protection circuit of RRU receiver and RRU receiver |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2724276A1 (en) * | 1994-09-07 | 1996-03-08 | Valeo Electronique | RHYTHM RECOVERY DEVICE, RECEIVER AND TRANSMISSION DEVICE COMPRISING THE SAME, AND RADIO FREQUENCY SIGNAL USING THE SAME |
| DE10228694A1 (en) | 2002-06-27 | 2004-01-22 | Bosch Rexroth Ag | Wien-Robinson oscillator |
| KR100739524B1 (en) * | 2007-04-09 | 2007-07-13 | 주식회사 룩센테크놀러지 | Sine wave oscillator with self start-up |
-
1978
- 1978-12-11 HU HUTE000918 patent/HU178124B/en not_active IP Right Cessation
-
1979
- 1979-10-19 CS CS709279A patent/CS221529B2/en unknown
- 1979-10-22 DD DD21636279A patent/DD146728A5/en unknown
- 1979-11-08 GB GB7938690A patent/GB2042840B/en not_active Expired
- 1979-11-14 DE DE19792945999 patent/DE2945999C2/en not_active Expired
- 1979-12-06 PL PL22018079A patent/PL123572B1/en unknown
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2017151290A1 (en) * | 2016-03-02 | 2017-09-08 | Qualcomm Incorporated | Systems and methods for compensating for variation in an amplitude-regulated oscillator |
| CN113037306A (en) * | 2019-12-25 | 2021-06-25 | 成都鼎桥通信技术有限公司 | Amplitude limiting protection circuit of RRU receiver and RRU receiver |
Also Published As
| Publication number | Publication date |
|---|---|
| DE2945999A1 (en) | 1980-06-12 |
| DE2945999C2 (en) | 1983-10-13 |
| CS221529B2 (en) | 1983-04-29 |
| DD146728A5 (en) | 1981-02-25 |
| HU178124B (en) | 1982-03-28 |
| PL220180A1 (en) | 1980-09-08 |
| PL123572B1 (en) | 1982-10-30 |
| GB2042840B (en) | 1983-04-13 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US4254382A (en) | Crystal oscillator temperature compensating circuit | |
| US3831117A (en) | Capacitance multiplier and filter synthesizing network | |
| US4358742A (en) | Transimpedance oscillator having high gain amplifier | |
| NL9201372A (en) | Temperature compensated oscillator circuit. | |
| US3435375A (en) | Controller having fet bridge circuit | |
| US3503010A (en) | Temperature compensating unit for crystal oscillators | |
| JPS644364B2 (en) | ||
| GB2042840A (en) | RC-bridge Oscillator | |
| US4072912A (en) | Network for temperature compensation of an AT cut quartz crystal oscillator | |
| US3641461A (en) | Temperature compensated crystal oscillator | |
| EP0434109B1 (en) | Voltage-controlled oscillator | |
| FI87868B (en) | SLINGFILTER FOR FREQUENCY SYNTHESISATOR | |
| US3047808A (en) | Integrator with means for compensating for capacity absorption effects | |
| GB1417069A (en) | Circuit arrangement for converting a bridge unbalance into a frequency variation | |
| EP0096587B1 (en) | Temperature compensating circuit for oscillator | |
| US3906381A (en) | Integrator circuit and low frequency two phase oscillator incorporating same | |
| US3303436A (en) | Subminiature crystal oscillator of high stability | |
| GB781374A (en) | Improvements in or relating to resonant electronic circuits | |
| US6340913B1 (en) | Filter circuit with positive feedback loop | |
| JPH0548643B2 (en) | ||
| US3942131A (en) | Low frequency two phase oscillator including variable feedback integrator circuits | |
| JPS6077504A (en) | Oscillator | |
| US4546270A (en) | Sample and hold droop compensation circuit | |
| JP3123581B2 (en) | High-speed composite inverting amplifier | |
| US3564396A (en) | Four-pole network employed as an improved compensating circuit for a capacitor's dielectric absorption losses |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |