Browse Prior Art Database

Oscillator

IP.com Disclosure Number: IPCOM000092217D
Original Publication Date: 1968-Oct-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 25K

Publishing Venue

IBM

Related People

Neal, DM: AUTHOR [+2]

Abstract

In this oscillator circuit having automatic gain control, transistors T1 and T2 define a high-gain differential amplifier. This, for small signals, supplies current to oscillator network 10. This network is connected to the collector of T1 and produces oscillations which increase in magnitude with time. As the voltage signal at the base of T2 becomes large, T1 begins to turn off on the positive voltage swings and T2 begins to turn off on the negative voltage swings. When this occurs, T1 and T2 cease to be small signal amplifiers and become exclusively current switches which supply to network 10 a square wave of current whose magnitude is independent of the signal at the base of T2.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 96% of the total text.

Page 1 of 2

Oscillator

In this oscillator circuit having automatic gain control, transistors T1 and T2 define a high-gain differential amplifier.

This, for small signals, supplies current to oscillator network 10.

This network is connected to the collector of T1 and produces oscillations which increase in magnitude with time. As the voltage signal at the base of T2 becomes large, T1 begins to turn off on the positive voltage swings and T2 begins to turn off on the negative voltage swings. When this occurs, T1 and T2 cease to be small signal amplifiers and become exclusively current switches which supply to network 10 a square wave of current whose magnitude is independent of the signal at the base of T2. When operating in the current switch mode, T1 turns on each cycle just long enough to replace the energy dissipated in the resistor over that cycle. The magnitude of the voltage signal at the collector of T1 is regulated to a value determined by the value of its collector current and the value of resistor 11. The frequency of oscillation is controlled by crystal 12 which also serves as a coupling capacitor to output transistor T3.

The latter is connected as an emitter-follower and appears as a constant impedance to crystal 12. Resistor 11 provides the proper voltage level at the collector of T1 and, in addition, serves to reduce the tendency of network 10 from changing the frequency of crystal 12 when the frequency of such crystal and the circuit is not identical.

1

Page 2 o...