The DF91 is a is a miniature screened pentode for dry battery operation. It was designed for broadcast radio reception and is a variable μ RF device.

See also 1T4

The thin glass tube envelope is 17 mm in diameter and, excluding the B7G base pins, is 47 mm tall.

 
Pin Connections

B7G	1	2	3	4	5	6	7
	f-	a	g2	ic	f-	g1	f+

 
Absolute Maximum Operating Conditions

Pentode	Vh	Ah	Va	Vs	Vg	mAa	mAs	ra	gm
	1.4	0.05	90	67.5	0	3.5	1.5	0.5M	0.9

Thanks to Frank Philipse for supplying the above datasheet

This exhibit was last updated on 06 July 2007 {find valves by name}