>A cathode driven configuration doesn't inherently cause excessive grid
>current. If proper grid and screen voltages are supplied, the grid current
>is a function of grid bias voltage and drive level, just as in grid driven
** The thing that makes tetrode RF grounded-grid different from tetrode
grid-driven is that in grid-driven, the RF driving signal exists between
the RF-grounded screen and the control grid. However, in grounded-grid
configuration, there is Zero signal V between the grid and the screen -
g1/g2 amplification is zero. Also, in grid-driven config., there is zero
current and a moderate amount of screen current The reason is that the
grid operates in the negative region - which does not attract electrons,
however, the screen is positive, which does attract electrons..
> The higher the drive level, the higher the peak cathode voltage, the higher
>the peak grid voltage, the higher the peak grid current and the higher the
>average grid current (which is what we are measuring).
>The cathode driven configuration also offers the same negative feedback
>benefits as in a triode cathode griven (grounded grid) circuit, primarily a
>reduction in odd order products.
>One of the main reasons grid drive circuits are not popular for vhf/uhf
>amplifiers is because the input capacitance is the sum of grid to cathode and
>to screen capacitances, almost double the input capacitance of a cathode
>circuit consisting of cathode to grid capacitance only.
** good point The trade-off is difficulty in obtaining wide freq.
coverage with g-g.
>currents are higher and resulting I^2 X R losses are higher in the input
>At h.f. these effects are minimal and either configuration works fine. The
>bulky grid termination resistor can be eliminated with the cathode drive
>As always, "you pays your money and takes your choice"!
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