Series Triode Voltage Regulator

Series Triode Voltage Regulator

The series triode voltage regulator is similar to series transistor regulator except that here triode and glow tube are used instead of transistor and zener diode.

Circuit Diagram of  Series Triode Voltage Regulator

You can see the circuit diagram of a series triode voltage regulator below . The resistance R and glow tube (V.R.) help to maintain constant potential across the load. A potentiometer Rp is connected across the glow tube and its variable point is connected to the grid of the triode.

Series Triode Voltage Regulator

Working of Series Triode Voltage Regulator

The d.c. input Vin from the unregulated power supply is fed to the voltage regulator. The circuit will maintain constant output voltage (Vout) inspite of changes in load current or input voltage. The output voltage is given by :

Vout = Ep + Eg

Now, Ep is constant because the glow tube is operating in the normal glow region. Also grid voltage Eg is constant because it hardly depends upon plate current. Therefore, output will remain accurately fixed at one value. Any increase in the output voltage causes greater voltage drop across the limiting resistance R, tending to restore the output voltage to the original value.

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