A pentode is an electron tube having five electrodes.

History and characteristics

The pentode in 1926 by Bernard Tellegen, an employee at the Philips Research Laboratory, invented and patented together with Gilles Holst.

In addition to the anode and cathode, the control grid and the screen grid of the tetrode, it has one end connected to the cathode suppressor grid. This keeps the secondary emission from the anode screen grid.

The flat characteristic of pentode shows that the anode is so screened by the additional grid, that a change in the anode voltage has no more influence on the anode current. It is only dependent on the bias voltage on the control grid:

Pentode characteristic

Wherein a substantially higher gain.

Similarly behaves the Strahlpentode, which was called for licensing reasons Beam power tetrode.


Audio amplifier tube EL34 Mullard of

QUAD II audio amplifier with two EF86 as a driver and two Strahlpentoden KT66 as the final stage

Video Verstärkerpentode 12BY7A

Macro shot of a EF91

Decomposed EL84 left to right: cathode, control grid, screen grid, suppressor grid, anode

Sub-micro tubes ECG 5639