Patent ID: 7206405

Claim:
A high voltage analog circuit for a subscriber line interface circuit comprising: an input signal receiving unit, that is operative to condition and interface input voice and low voltage signaling and ringing signals, supplied from a digitally programmable signal generation and processing unit; a multi-mode, multigain tip/ring amplifier unit, having tip and ring outputs thereof adapted to be coupled to tip and ring conductors of a subscriber loop pair, and inputs coupled to receive and amplify said voice and low voltage signaling and ringing signals from said input signal receiving unit, in accordance with a selected mode of operation and gain of said subscriber line interface circuit; and a biasing unit, to which power for operating said high voltage analog circuit is coupled, and being operative to controllably couple bias voltages to said tip and ring amplifier sections of said multi-mode, multi-gain tip/ring amplifier unit in accordance with the mode of operation of said subscriber line interface circuit, and wherein, for high gain operation of said multi-mode, multi-gain tip/ring amplifier unit, said biasing unit is operative to switchably couple a relatively small voltage to a reference voltage port of said dual gain multi-mode tip/ring amplifier unit, such that only a relatively small input current is necessary to deflect said multimode, multigain tip/ring amplifier unit from its reference voltage value, and wherein said biasing unit contains a set of switchable voltage divider networks coupled between a relatively low magnitude reference voltage and a battery supply switch unit that is operative to selectively couple first and second battery voltages to said biasing unit, and wherein said biasing unit is operative to switchably decouple a tip path voltage divider network from said battery supply switch unit, while coupling said relatively low magnitude reference voltage through said decoupled tip path voltage divider network to a reference voltage port of a tip path front end transconductance circuit of said multi-mode, multi-gain tip/ring amplifier unit.