Electrical Engineering

Electrical engineering (sometimes referred to as electrical and electronic engineering) is a engineering discipline that deals with the study and/or application of electricity, electronics and electromagnetism. The field first became an identifiable occupation in the late nineteenth century after commercialization of the electric telegraph and electrical power supply. The field now covers a range of sub-studies including those that deal with power, electronics, control systems, signal processing and telecommunications.

The term electrical engineering may or may not encompass electronic engineering. Where a distinction is made, electrical engineering is considered to deal with the problems associated with large-scale electrical systems such as power transmission and motor control, whereas electronic engineering deals with the study of small-scale electronic systems including computers and integrated circuits. Another way of looking at the distinction is that electrical engineers are usually concerned with using electricity to transmit energy, while electronics engineers are concerned with using electricity to transmit information.

Voltage Controlled Oscillators

What are voltage controlled oscillators?
The voltage controlled oscillator which is more commonly known, a vco, is an oscillator which works on the principal of variable capacitance or tuning with a varactor diode. The voltage controlled oscillator is tuned across its band by a "clean" dc voltage applied to the varactor diode to vary the net capacitance applied to the tuned circuit.

What are Varactor or Tuning Diodes
These types of diodes work on the principle that all diodes exhibit some capacitance. When the voltage applied across the diodes changes the capacitance developed across it also changes.

Temperature compensated voltage controlled oscillator
A VCO with temperature compensation is achieved using reverse biased diodes. The VCO includes an amplifier that provides the required signal gain, a resonator tank circuit that provides the required phase shift, and at least one frequency tuning circuit for tuning the frequency of the oscillator signal. Each frequency tuning circuit includes at least one tuning capacitor and at least one MOS pass transistor that connects or disconnects the tuning capacitor(s) to/from the resonator tank circuit. Each reverse biased diode may be a parasitic diode that is formed at a drain or source junction of a MOS transistor. The reverse biased diodes have capacitance that can be controlled by a reverse bias voltage to compensate for drift in the VCO oscillation frequency over temperature.