GB2217939A - An integrated negative resistance oscillator circuit - Google Patents
An integrated negative resistance oscillator circuit Download PDFInfo
- Publication number
- GB2217939A GB2217939A GB8810235A GB8810235A GB2217939A GB 2217939 A GB2217939 A GB 2217939A GB 8810235 A GB8810235 A GB 8810235A GB 8810235 A GB8810235 A GB 8810235A GB 2217939 A GB2217939 A GB 2217939A
- Authority
- GB
- United Kingdom
- Prior art keywords
- oscillator
- transistors
- pair
- circuit
- negative impedance
- 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
- H03K—PULSE TECHNIQUE
- H03K3/00—Circuits for generating electric pulses; Monostable, bistable or multistable circuits
- H03K3/02—Generators characterised by the type of circuit or by the means used for producing pulses
- H03K3/26—Generators characterised by the type of circuit or by the means used for producing pulses by the use, as active elements, of bipolar transistors with internal or external positive feedback
- H03K3/28—Generators characterised by the type of circuit or by the means used for producing pulses by the use, as active elements, of bipolar transistors with internal or external positive feedback using means other than a transformer for feedback
- H03K3/281—Generators characterised by the type of circuit or by the means used for producing pulses by the use, as active elements, of bipolar transistors with internal or external positive feedback using means other than a transformer for feedback using at least two transistors so coupled that the input of one is derived from the output of another, e.g. multivibrator
- H03K3/282—Generators characterised by the type of circuit or by the means used for producing pulses by the use, as active elements, of bipolar transistors with internal or external positive feedback using means other than a transformer for feedback using at least two transistors so coupled that the input of one is derived from the output of another, e.g. multivibrator astable
- H03K3/2823—Generators characterised by the type of circuit or by the means used for producing pulses by the use, as active elements, of bipolar transistors with internal or external positive feedback using means other than a transformer for feedback using at least two transistors so coupled that the input of one is derived from the output of another, e.g. multivibrator astable using two active transistor of the same conductivity type
-
- 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
- H03B7/00—Generation of oscillations using active element having a negative resistance between two of its electrodes
- H03B7/02—Generation of oscillations using active element having a negative resistance between two of its electrodes with frequency-determining element comprising lumped inductance and capacitance
- H03B7/06—Generation of oscillations using active element having a negative resistance between two of its electrodes with frequency-determining element comprising lumped inductance and capacitance active element being semiconductor device
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03K—PULSE TECHNIQUE
- H03K3/00—Circuits for generating electric pulses; Monostable, bistable or multistable circuits
- H03K3/02—Generators characterised by the type of circuit or by the means used for producing pulses
- H03K3/023—Generators characterised by the type of circuit or by the means used for producing pulses by the use of differential amplifiers or comparators, with internal or external positive feedback
- H03K3/0231—Astable circuits
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Inductance-Capacitance Distribution Constants And Capacitance-Resistance Oscillators (AREA)
Abstract
The invention provides a negative resistance oscillator for use as a local oscillator in an integrated VHF/UHF tuner circuit. The circuit is symmetrical and balanced, and requires only two external pins for making connection to an external tuning circuit. <IMAGE>
Description
ON- CHIP OSCILLATOR CIRCUIT
This invention relates to an integrated circuit fabricated on a chip and including an oscillator circuit. The invention is particularly directed to such an oscillator circuit for use in a radio-frequency (R.F.) tuning system such as a VHF/UHF television tuner circuit.
Heretofore, due to the size of and spacing of the components of the oscillator in an integrated circuit, radiation levels from the
oscillator have been unacceptable and either further components or
greater spacing (with less efficient use of chip area) have been
necessary to constrain the radiation to acceptable levels.
It is an object of the present invention to provide an improved
on-chip oscillator circuit wherein oscillator radiation is greatly
reduced.
According to the present invention, there is provided a
negative impedance oscillator, forming part of an integrated circuit,
comprising a first pair of transistors to the bases of which a
differential input may be applied, and a second pair of emitter
follower transistors the bases of which are respectively dc cross
coupled to the emitters of the first transistors, the second pair of
transistors forming a differential pair, and the collectors of the first
transistors providing output of the oscillator.
The invention will be described further, by way of example,
with reference to the accompanying drawings, in which:
Figure 1 is a circuit diagram of a negative impedance oscillator
circuit arranged for fabrication on a chip as part of an integrated
circuit;
Fligure 2 is an explanatory diagram of part of the circuit of
Figure 1; and
Figure 3 is a circuit diagram of a preferred negative impedance oscillator according to the present invention.
Referring firstly to Figures 1 and 2, there is shown a negative impedance oscillator circuit in accordance with the present invention which is readily fabricated on a silicon chip using standard techniques. The circuit comprises a pair of NPN transistors T1 and T2 to the bases of which a diferential input voltage i A V is respectively applied. As emitter followers, NPN transistors T3 and T4 form a differential pair having a common current source IEE. The input volltages +tvV and -AV are cross dc coupled to the bases of the transistors T3 and T4 as shown.Transistors T1 and T2 have respective dc current sources 1e1 and 1e2 and the collectors of the transistors T1 and T2 provide the oscillator output currents il and i2.
The differentially applied input voltage signals -AV and +AV switch the transistors T3 and T4 causing corresponding swings on the emitters of the transistors T1 and T2 and on the bases of the opposite transistors T4 and T3 of the differential pair. If the input impedance equals the output (load) impedance, the circuit will oscillate. Further, it can be shown that such a circuit operates as a non-linear (with respect to output current amplitude) negative impedance oscillator.
Due to the symmetry of the circut and the fact that on-chip components can be very closely matched in characteristics, a well balanced oscillator with very low radiation levels results.
Referring to Figure 2, and making the following assumption:
1) the base currents of the transistors T3 and T4 can be ignored;
2) the transistors T3 and T4 do not fully switch but operate over the linear part of their characteristics; and
3) modulation of the base/emitter voltages of transistors T1 and T2 can be ignored.
On the basis of these assumptions, the current i2 flowing in the collector of transistor T2 is related to the transconductance gm4 of the transistor T4. This can be expressed as follows:
i2 = - gm4. #V 1 where - AV is the voltage applied to the base of transistor T4 and gm4 =IEE/2.VT4 2.
where IEE/2 is the collector/emitter current of transistor T4 and VT4 is the collector /emitter voltage thereacross.
To derive R1 in (the input resistance of the transistor T2), the base current ib2 of the transistor T2 must be included.
ib2 = i2/ss2 Where B is the known parameter relating collector current to base current for a particular transistor.
R'in - AV/ib = B#V/i2 4.
Rm - - BAV/gm4 . AV =
The total input resistance RIN of the circuit of Figure 1 is then
RIN = 2. Rlin - - 2ss/gm4 and from equation 3.
RIN ~ - 4 BVT/IEE
SPICE (Simulation Program for Integrated Circuit Evaluation) simulations provide reasonable agreement with the expressions derived above
A circuit as shown in Figure 3 was constructed. The oscillator so formed operated at 700 MHz and showed little sign of previous troublesome radiation. Degeneration resistors R1 and R2 were included in the emitters of T4 and T3 to increase the value of - RIN.
The oscillator outputs (at the collectors of T1 and T2), provide isolation of the output currents from the tank ciruit 11 applying the input to the bases of T1 and T2. The oscillator output level can be adjusted in accordance with the demands of the load circuit 10. The tank circuit 11 may be fixed or tunable so that a fixed frequency or controllable frequency of oscillation may be obtained.
It was found that, in practice, some hysteresis was introduced due to full switching of the transistors T3 and T4 causing modulation of the base/emitter voltages of the transistors T1 and T2.
Nevertheless, the symmetrical circuit arrangement and the extremely good component matching obtained due to integrated circuit fabrication provided low levels of radiation and a well balanced output.
It should be noted that a further advantage arises in that only two package pin connections (connecting to the external tank circuit 11) are required for this arrangement instead of four package pins previously required.
The preferred embodiment shown in Figure 3 has thus many advantages and can provide, for example, a voltage controlled local oscillator for use in a T.V. tuner circuit.
Claims (9)
1. A negative impedance oscillator, forming part of an integrated circuit, comprising a first pair of transistors to the bases of which a differential input may be applied, and a second pair of emitter follower transistors the bases of which are respectively dc cross coupled to the emitters of the first transistors, the second pair of transistors forming a differential pair, and the collectors of the first transistors providing output of the oscillator.
2 An oscillator as claimed in claim 1 wherein the transistors of the first and second pair are NPN transistors.
3. An oscillator as claimed in claim 1 or 2 further including a degeneration resistor in the emitter of each transistor of the second pair.
4. An oscillator as claimed in claim 1, 2 or 3 wherein the differential input is supplied by an external tank circuit.
5. An oscillator as claimed in claim 4 wherein the tank circuit is tunable.
6. An oscillator as claimed in claim 4 or 5 wherein the tank circuit provides voltage control of the oscillator.
7. An oscillator as claimed in any preceding claim including only two external package pins whereto the differential input is applied.
8. A negative impedance oscillator substantially as hereinbefore described with reference to and as illustrated in the accompanying
drawings.
9. A television tuner circuit including a negative impedance
oscillator as claimed in any preceding claim.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8810235A GB2217939B (en) | 1988-04-29 | 1988-04-29 | Negative impedance oscillator circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8810235A GB2217939B (en) | 1988-04-29 | 1988-04-29 | Negative impedance oscillator circuit |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB8810235D0 GB8810235D0 (en) | 1988-06-02 |
| GB2217939A true GB2217939A (en) | 1989-11-01 |
| GB2217939B GB2217939B (en) | 1992-07-22 |
Family
ID=10636139
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8810235A Expired - Fee Related GB2217939B (en) | 1988-04-29 | 1988-04-29 | Negative impedance oscillator circuit |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2217939B (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0689283A1 (en) * | 1994-06-24 | 1995-12-27 | Plessey Semiconductors Limited | Tunable oscillator arrangement |
-
1988
- 1988-04-29 GB GB8810235A patent/GB2217939B/en not_active Expired - Fee Related
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0689283A1 (en) * | 1994-06-24 | 1995-12-27 | Plessey Semiconductors Limited | Tunable oscillator arrangement |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2217939B (en) | 1992-07-22 |
| GB8810235D0 (en) | 1988-06-02 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| 732 | Registration of transactions, instruments or events in the register (sect. 32/1977) | ||
| 732E | Amendments to the register in respect of changes of name or changes affecting rights (sect. 32/1977) | ||
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 20050429 |