This valve is an output beam tetrode (Pen45) and a pair of diodes together in a single envelope, and dates from 1938. These multiple valves were designed to be signal and AGC detectors in superhet receivers and additionally to do the whole audio amplification to speaker levels. This saved cost to the set makers.

The PEN45DD has rather more gain than the Pen453DD and was correspondingly more successful. However, even with the additional pentode gain the overall audio amplification was insufficient to support a gramophone input socket or for a radiogram version of the set. Use of a double-diode triode plus a Pen45 therefore remained the norm except in the cheapest sets.

The anode load was 5,000 Ohms.

The classic envelope is 42 mm in diameter and, excluding the MO base pins, is 107 mm tall.

 
Pin Connections

MO	1	2	3	4	5	6	7	8	tc
	h	k	a	g2	a(d2)	m	a(d1)	h	g1

 
Absolute Maximum Operating Conditions

Pentode	Vh	Ah	Va	Vs	Vg	mAa	ra	gm	Pout
	4.0	2.0	250	250	-8.5	40	40,000	9.0	4.8W

Thanks to Frank Philipse for supplying the above datasheet

This exhibit was last updated on 02 December 2007 {find valves by name}