High operational voltage

Warm-up time is required

Bandwidth of light is $4000\mathop {\rm{A}}\limits^{\rm{o}}-7000 \mathop {\rm{A}}\limits^{\rm{o}}$

Fast on-off switching

$P=1, Q=1, R=0$

$P=0, Q=1, R=0$

$P=1, Q=0, R=1$

$P=1, Q=1, R=1$

a $p-n-p$ transistor

an n-p-n transistor

a p-n junction diode

an inductor

$0^{\circ}$

$90^{\circ}$

$120^{\circ}$

$180^{\circ}$