Rob's web

Home - Techniek - Electronica - Radiotechniek - Radio amateur bladen - QST - 807 grounded-grid class B stage

A note from G3FHL mentions that he and G3BQQ have used a triode-connected 807 as a linear amplifier in the circuit shown in Fig. 1. The grounded-grid stage has a very low input impedance (around 200 ohms), which accounts for the tapping down on the grid coil. Connected this way, the 807 becomes a zero-bias tube, at some plate voltage that wasn't mentioned. Since the subject of grounded-grid amplifiers gets kicked around a lot by the s.s.b. gang, the circuit is passed along for anyone who would like to try it.

Fig 1
Fig. 1. Some of the s.s.b. Ga are using triode-connected 807s as zero-bias grounded-grid Class B amplifiers. The low input impedance of the stage requires that the input coil be tapped down, as shown here.