# Clapp oscillator

﻿
Clapp oscillator

The Clapp oscillator is one of several types of electronic oscillator constructed from a transistor (or vacuum tube) and a positive feedback network, using the combination of an inductance (L) with a capacitor (C) for frequency determination, thus also called LC oscillator.

It was published by James Kilton Clapp in 1948.[1] According to Vačkář,[2] oscillators of this kind were independently developed by several inventors, and one developed by Gouriet had been in operation at the BBC since 1938.

Clapp Oscillator (direct-current biasing network not shown)

Referring to the notional circuit in the figure, the network comprises a single inductor and three capacitors. Capacitors C1 and C2 form a voltage divider that determines the amount of feedback voltage applied to the transistor input. The Clapp oscillator is a Colpitts oscillator that has an additional capacitor placed in series with the inductor. The oscillation frequency in hertz (cycles per second) for the circuit in the figure, which uses a field-effect transistor (FET), is

$f_0 = {1 \over 2\pi} \sqrt{ {1 \over L} \left( {1 \over C_0} + {1 \over C_1} + {1 \over C_2} \right)} \ .$

A Clapp circuit is often preferred over a Colpitts circuit for constructing a variable frequency oscillator (VFO). In a Colpitts VFO, the voltage divider contains the variable capacitor (either C1 or C2). This causes the feedback voltage to be variable as well, sometimes making the Colpitts circuit less likely to achieve oscillation over a portion of the desired frequency range. This problem is avoided in the Clapp circuit by using fixed capacitors in the voltage divider and a variable capacitor (C0) in series with the inductor.

## References

1. ^ J. K. Clapp, "An inductance-capacitance oscillator of unusual frequency stability", Proc. IRE, vol. 367, pp. 356-358, Mar. 1948.
2. ^ Jiri Vackar, LC Oscillators and their Frequency Stability, TESLA Report 1949, ch. 4, [1]
• Ulrich L. Rohde, Ajay K. Poddar, Georg Böck "The Design of Modern Microwave Oscillators for Wireless Applications ", John Wiley & Sons, New York, NY, May, 2005, ISBN 0-471-72342-8.
• George Vendelin, Anthony M. Pavio, Ulrich L. Rohde " Microwave Circuit Design Using Linear and Nonlinear Techniques ", John Wiley & Sons, New York, NY, May, 2005, ISBN 0-471-41479-4.

Wikimedia Foundation. 2010.

### Look at other dictionaries:

• Clapp — may refer to: People named Clapp or Clap: Clapp (surname), predominantly found in England and the United States Allen Clapp, an American rock singer in the band, The Orange Peels Asa Clapp, an American politician (d.1891) Austin Clapp, an… …   Wikipedia

• Clapp-Schaltung — Fig.1: Clapp Oszillator mit Röhre Fig. 2: Clapp Oszillator mit Tr …   Deutsch Wikipedia

• Colpitts oscillator — Early schematic of a Colpitts circuit, using a vacuum tube, redrawn from the patent publication. A Colpitts oscillator, invented in 1920 by American engineer Edwin H. Colpitts, is one of a number of designs for electron …   Wikipedia

• Vačkář oscillator — A Vackář oscillator is a variation of the split capacitance oscillator model. It is similar to a Colpitts oscillator or a Clapp oscillator in this respect. It differs in that the output level is relatively stable over frequency, and has a wider… …   Wikipedia

• Electronic oscillator — An electronic oscillator is an electronic circuit that produces a repetitive electronic signal, often a sine wave or a square wave.A low frequency oscillator (LFO) is an electronic oscillator that generates an AC waveform between 0.1 Hz and 10 Hz …   Wikipedia

• Hartley oscillator — The Hartley oscillator is an LC electronic oscillator that derives its feedback from a tapped coil in parallel with a capacitor (the tank circuit ). Although there is no requirement for there to be mutual coupling between the two coil segments,… …   Wikipedia

• Armstrong oscillator — The Armstrong oscillator (also known as Meissner oscillator) is named after the electrical engineer Edwin Armstrong, its inventor. It is sometimes called a tickler oscillator because the feedback needed to produce oscillations is provided using a …   Wikipedia

• Scientific phenomena named after people — This is a list of scientific phenomena and concepts named after people (eponymous phenomena). For other lists of eponyms, see eponym. NOTOC A* Abderhalden ninhydrin reaction Emil Abderhalden * Abney effect, Abney s law of additivity William de… …   Wikipedia

• Oscillation — For other uses, see oscillator (disambiguation) and oscillation (mathematics). An undamped spring–mass system is an oscillatory system. Oscillation is the repetitive variation, typically in time, of some measure about a central value (often a… …   Wikipedia

• List of electronics topics — Alphabetization has been neglected in some parts of this article (the b section in particular). You can help by editing it. This is a list of communications, computers, electronic circuits, fiberoptics, microelectronics, medical electronics,… …   Wikipedia