Jerry Peters wrote:
Kaz Kylheku wrote:
On 2014-01-28, wrote:
If a diode is not active, why ? You can modulate with it. You can switch with it. This can be done with solid state diodes or otherwise.
A diode is not active by itself, because it's a two-port circuit. There is no
way for it to have an input which controls an output.
Switching diode which switches an AC signal with a DC signal. It's
been done for years.
PIN diode which can switch or attenuate an RF signal with a DC
current.
We used them as band switches in a low noise synthesizer. A DC
voltage would turn the diode on to short out part of the inductor,
raising the center frequency of the VCO. Breaking the 360-510 MHz into
four overlapping segments allowed for more linear and reduced the
effects of noise on the tuning voltage that controlled the tuning.