By changing the bias current through a PIN diode, it's possible to quickly change the RF resistance.
Leakage through the Marx resistors needs to be compensated by a small bias current through the generator.
The current determined by this resistor acts also as a reference for the other bias currents used in the chip.
A bias current is allowed to flow into the base via VR1 and R1.
After applying microwave power, the bias current is reduced to return the bolometer to its resistance in the absence of microwave power.
If the bias current is shunted to ground (low logic level), the transistor turns off and the collector floats (high logic level).
These minima exist for bias currents , i.e. for currents below the critical current.
With most of the bias current flowing through the amplifier, the non-superconducting region cools and returns to the superconducting state.
The characteristics of the recording system change quite markedly as the level of the bias current is changed.
The current mirror is used to provide bias currents and active loads to circuits.