The CV303 is the UK government designation for the commercial EF22 and is an early example of an all glass construction amplifier pentode. In this valve the whole envelope is encased in a screening aluminium can.

In the above picture the base can be clearly seen. The short pins are of hardened construction.

The pentode is described as of variable mu. That is that the characteristic curve is such that different amplifications are possible by varying the grid bias point. Mullard describe the EF22 as primarily intended for use in DC/AC mains operated equipment in the role of RF or IF amplifier.

The wide glass tube envelope is 28 mm diameter and 65 mm tall, excluding the B8B base pins and spigot.

 
Pin Connections

B8B	1	2	3	4	5	6	7	8
	g3	s	g2	g1	a	k	h	h

 
Absolute Maximum Operating Conditions

Pentode	Vh	Ah	Va	Vs	Vg	mAa	mAs	ra	gm
	6.3	0.2	250	100	-2.5	6	1.7	1.2M	2.0

This exhibit was last updated on 24 April 2009