This the ubiquitous amplifier stage using a single triode. To compute the DC operating point, enter the values of Vb, Ra and Rk.
Manage to obtain an anode voltage comprised within [1/2 … 1/3] of supply voltage.
To cleverly design such a stage, you may refer to http://www.valvewizard.co.uk/gainstage.html
“Small signal” estimations are indicated for tube internal resistance, transconductance in mA/V and voltage gain.
They are given for two conditions: the cathode resistor is decoupled (by a capacitor) or not.
The voltage gain does not take into account an external load resistor.
Note: the grid resistor normally found
between grid and cathode is not taken
into account here, as it has null or
neglectible influence on the operating point.