How do I switch a PIN diode using a TTL control signal?
The schematic contains the PIN diode approx. DC model, there are no high frequency components on it.
The 2mA from the -400V can be set by R3.

The 200mA PIN diode forward current is set by R1.

DC Transfer Characteristic:

The switching times are set by L1.

If the 5V isn't enough to PIN diode forward current, the power supply voltage of U1 can be increased up to 18V. But afterwards you have to set R1 for the 200mA again.
The input voltage remains TTL and 5/3V CMOS compatible at every power supply voltage (U1).