Device and method for biasing a transistor amplifier

A method for biasing a transistor amplifier with a DC-voltage signal, said amplifier having a first input terminal, a second input terminal, and an output terminal coupled to the second input terminal, the method comprising:

• operatively coupling a sensor capacitor and parallel impedance transistor to the first input terminal, the transistor and capacitor forming a low-pass filter, and a biasing circuit to the impedance transistor, the biasing circuit including a cascaded current arrangement configured to subdivide a reference current into smaller currents for selectively generating voltage potentials for biasing the impedance transistor to adjustably filter a noise component of the DC-voltage signal via the low-pass filter before the DC-voltage signal is provided to the first input terminal;
• and
• selectively adjusting the DC-voltage signal with the biasing circuit to filter the noise component.

A device for biasing a transistor amplifier with a DC-voltage signal, the transistor amplifier having a first input terminal, a second input terminal, and an output terminal coupled to the second input terminal, wherein said device comprises:

• an impedance transistor forming part of a low-pass filter;
• and
• a biasing circuit configured to controllably vary the DC-voltage signal for operatively biasing the amplifier, the biasing circuit including a cascaded current arrangement configured to subdivide a reference current into smaller currents for selectively generating voltage potentials for biasing the impedance transistor to adjustably filter a noise component of the DC-voltage signal via the low-pass filter before the DC-voltage signal is provided to the first input terminal.

A low-pass filter adapted for use in filtering out a voltage ripple in a supply voltage signal, the voltage ripple being generated by a voltage multiplier device during voltage step-up conversion of the supply voltage signal before said supply voltage signal is fed to a capacitive sensor, the low-pass filter including a capacitor operatively coupled with a first and second diode, said first and second diodes being adapted for operative coupling in parallel between a terminal of the capacitor and an output terminal of the voltage multiplier device, said diodes being arranged in reverse polarity relative to each other in parallel.