The EF9 is a variable μ amplifier pentode.

The variable μ amplifier pentode would be used in the AGC controlled stages of superhet receivers, IF and for HF receivers also RF amplifiers.

The EF9 is electrically identical to the IO based EF39, additionally the EF9 is pin compatible with the EF5 and has a higher voltage gain.

Our exhibit is unused, and has the distinctive red painted Mullard external metalisation screening.

The classic envelope is 29 mm in diameter and, excluding the Ct8 base pins, is 84 mm tall.

 
Pin Connections

Ct8	1	2	3	4	5	6	7	8	tc
	m	h	h	k	g3	-	g2	a	g1

 
Absolute Maximum Operating Conditions

Pentode	Vh	Ah	Va	Vs	Vg	mAa	mAs	ra	gm
	6.3	0.2	250	250	-2.5	6	1.7	1.5M	2.2

Thanks to Frank Philipse for supplying the above datasheet

This exhibit was last updated on 11 July 2007 {find valves by name}