constant voltage source

A constant voltage source is an electronic circuit which supplies a constant voltage independent of the load.

The basic condition for a constant voltage is an internal resistance( Ri) of the voltage source that is as close to zero as possible and a load resistance (Rl) that is significantly greater than the internal resistance (Ri "Rl). This basic condition is fulfilled to some extent in batteries and rechargeable batteries: The internal resistance is extremely low and the terminal voltage is thus largely independent of the load.

Electronic constant voltage sources are designed as feedback control circuits in which the smallest changes in the load voltage are fed back and used to compensate for any voltage changes. Zener diodes, whose reference voltage is compared with the load voltage, serve as reference elements. The control loops and control circuits are realized by transistor circuits, field effect transistors( FET) or differential amplifiers.