Oscillator

The Colpitts oscillator is one of the standard circuits of electronics and has been such almost from the day of its invention. Research engineers at Bell began their development work of the new triode (De Forest's audion) and its use in circuitry in 1912 when AT&T paid De Forest $50,000 for the right to use the triode as a telephone repeater. In 1914 they paid another $90,000 for the radio receiver rights to the triode, marking the start of electronic circuits.

Progress was rapid in the early years. The first important circuit was the positive-feedback, or regenerative, amplifier and 1913 saw many claimants to its invention⁷ in both America and Europe. Patent litigation in America dragged on for 20 years. But Colpitts invented one of the most famous and enduring of electronic circuits - the push-pull amplifier - on November 4, 1912.

Two years later came a circuit for producing and modulating high-frequency oscillations. This was an extension of work performed by G A Campbell, also at Bell, to discover the causes of "singing" in telephone amplifiers. Then, in March 1915, came the Colpitts oscillator, a month after Hartley had revealed the circuit named after him.

In the Second World War he was recalled from retirement to work on submarine warfare⁸, specifically on echo ranging systems and attack directors as "Head Technical Aide" of the National Defense Research Committee. For this effort, on April 5, 1948, he received the Medal for Merit, the USA's highest civilian award. The citation stated that it was for " outstanding services to the United States from June 1940 to June 1946". It seems ironic that before the war he had received a Japanese award, the Order of the Rising Sun, for a series of lectures he gave in Japan for the Iwadare Foundation.

In 1941 he also found time to accept the position of Director of the Engineering Foundation. This body, a joint agency of four US engineering societies, had been set up in 1914 for "the furtherance of research⁹ in science and engineering and the advancement of engineering and the good of mankind". It would seem that a man of Colpitts's calibre does not retire easily.

Colpitts died at the age of 77 at his home in Orange, New Jersey, USA, on March 6, 1949, after a lengthy illness and was survived by his second wife, Surah Grace. His first wife, Annie Dove Penney, whom he married in 1899, died in 1940. He was also survived by a son from the first marriage and by three brothers.

But long before his death he had been honoured as a distinguished telephone engineer of the pioneering period of continental and transcontinental wire and radio telephony, a respected administrator, holder of 24 patents, and a member of the relevant engineering and scientific institutes¹⁰ of America.

Task I

Speak on engineering problems Colpitts had to deal with while working for Bell Telephone Laboratories.

Task II

Tell the history of Colpitts’s biggest invention.

Task III

Describe Colpitts’s oscillator.