The FC4 from Mullard was the first British produced Octode. It was first made commercially in 1934.

The FC4 is a self oscillating mixer for frequency changing in radio superhet receivers. The oscillator has to generate 12 Volts peak to peak for correct operation. It would typically have used a 90 Volt oscillator anode voltage and up to 2.0 mA anode current. The oscillator would use g1 as control grid and g2 as anode. Of the six grids the final one was a suppressor, g3 and g5 would be screen grids, and the signal would be applied to g4, hence its position as top cap connection.

The classic envelope is 44 mm in diameter and, excluding the B7 base pins, is 112 mm tall.

 
Pin Connections

B7	1	2	3	4	5	6	7	tc
	g2	g1	g3,g5	h	h	m,k	a	g4

 
Absolute Maximum Operating Conditions

Octode	Vh	Ah	Va	Vs	Vg	mAa	mAs	gm
	4.0	0.65	250	70	-1.5	1.6	3.8	0.6

This exhibit was last updated on 02 December 2007