Butler oscillator
The Butler oscillator is a crystal-controlled oscillator that uses the crystal near its series resonance point. They are used where a simple low-cost circuit is needed which can oscillate at high frequencies (>50MHz[1]) by using overtones of a crystal, and also giving low phase noise.[2]
It was described by Butler in 1946 as the earthed grid oscillator, a derivative of the Hartley oscillator.[3] It is also known as the bridged-T oscillator or the grounded-base oscillator.[4]
Circuit operation
The classic Butler oscillator circuit is a two-stage circuit with two non-inverting stages, a grounded base stage and an emitter follower.[5] The crystal is inserted in series in the overall feedback path.[5]
The more common modern form of the circuit uses just the emitter follower stage.[1][6] The circuit may be analysed by considering it as an equivalent AC circuit with three parts. The emitter follower forms an amplifier with no phase shift. The crystal and its loading capacitor then produce a phase lag network, followed by the LC network of the resonant tank circuit. This then produces a phase lead, which overall meets the Barkhausen criteria for self-oscillation.[1]
The Butler circuit is a free-running or tuned oscillator. If the crystal is replaced temporarily with a low value resistor, the circuit will still oscillate at approximately the design frequency of the tank circuit. This allows the circuit to be set-up and adjusted initially without the crystal, and also encourages the selection of the correct crystal harmonic.[6] To avoid the circuit oscillating at the strong resonance of the crystal's fundamental, a small inductor may be placed in parallel with the crystal.[1][6]
Both the better-known Pierce and Colpitts oscillator circuits may be considered as derivatives of the Butler.[6][i]
References
Page Template:Reflist/styles.css has no content.
- ^ In the sense of circuit analysis, rather than historical origin.
- ^ a b c d Page Module:Citation/CS1/styles.css has no content."Butler Crystal Oscillator Design" (PDF). Understanding Quartz Crystals and Oscillators. pp. 237–247.
- ^ Page Module:Citation/CS1/styles.css has no content.Cushing, Richard; Swift, Steven. "A Discrete, Low Phase Noise, 125 MHz Crystal Oscillator for the AD9850 Complete Direct Digital Synthesizer" (PDF). Analog Devices. AN-419.
- ^ Page Module:Citation/CS1/styles.css has no content.Butler, F. (June 1946). "Series-Resonant Crystal Oscillators". Wireless Engineer. 23: 157–160.
- ^ Page Module:Citation/CS1/styles.css has no content.Karlquist, Richard (January 1999), A New Type of Balanced-Bridge Controlled Oscillator (PDF), Hewlett-Packard, HPL-1999-6, archived from the original (PDF) on 2016-03-03 Butler, Meacham, Sultzer, ...
- ^ a b Page Module:Citation/CS1/styles.css has no content.Gottlieb, Irving M. (1997), Practical Oscillator Handbook, Newnes, pp. 164–165, ISBN 0-7506-3102-3
- ^ a b c d Page Module:Citation/CS1/styles.css has no content."Crystal Theory" (PDF). Technical Notes. Somerset UK: EuroQuartz. Archived from the original (PDF) on 8 February 2015. Retrieved 8 February 2015.
Further reading
- Page Module:Citation/CS1/styles.css has no content.Carr, Joe (September 1999), "Crystals Made Clear I", Electronics World: 780–783
- Page Module:Citation/CS1/styles.css has no content.Carr, Joe (October 1999), "Crystals Made Clear II", Electronics World: 849–855
- Page Template:Citation/styles.css has no content.US 6741137, Sibrai, Andreas & Fritzwenwallner, Kurt, "High quality serial resonance oscillator", published Script error: No such module "auto date formatter"., issued Script error: No such module "auto date formatter".
- Page Template:Citation/styles.css has no content.US 3996530, Feistel, Claude Herbert & Gianos, Theodore, "Butler oscillator", published Script error: No such module "auto date formatter"., issued Script error: No such module "auto date formatter"., assigned to International Business Machines Corporation
External links
Page Module:Side box/styles.css has no content.Page Template:Sister project/styles.css has no content.
- Two-transistor Butler Script error: No such module "webarchive".
- Page Module:Citation/CS1/styles.css has no content."Technicana: Series Resonant Crystal Oscillators" (PDF), Radio Manufacturing and Broadcasting: 6–7, October 1946
Lua error in package.lua at line 80: module 'Module:Navbox/configuration' not found.
