gate bias of power amp?

I want to bias the gate of AMCOM power amplifiers,they need -1VDC(with 20mA capacity),how can I make -1V for gate bias from +22VDC?
The needed drain voltage for power amp is +20V.

It's quite easy to design a low power negative voltage supply.

You need the following:
Oscillator -- Output halfbridge stage -- Diode/capasitor bridge to get the negative voltage.

You need a voltage divider on the end.

can I use a micro like as ATtiny45 and its PWM to control output negative supply?

Is it low ripple on output to not produce spur at output of rf power amp?